Previous studies have examined the effects of red light (R) on phototropism of maize ( Zea mays L. cv. Royaldent Hit 85) coleoptiles. The R effect on time-dependent phototropism (TDP) was further studied by characteri...Previous studies have examined the effects of red light (R) on phototropism of maize ( Zea mays L. cv. Royaldent Hit 85) coleoptiles. The R effect on time-dependent phototropism (TDP) was further studied by characterizing its fluence-response relationship. The results showed the R effect was a low-fluence-response, unlike those on pulse-induced phototropisms that show a very-low-fluence-response mode. A subsequent pulse of far-red light (FR) could reverse the R effect. TDP responsiveness, however, recovered as the following FR was extended, The FR-dependent increase in TDP responsiveness was obtained even coleoptiles were pretreated only with FR. It suggested that TDP responsiveness could also be established in response to a FR signal. The fluence-response relationship for the effect of FR was then investigated. The effect of FR depended on the time of irradiation and required high photon fluences. Because reciprocity was invalid at the higher fluence range, the effect of FR would be a high-irradiance-response mode. Relation between phytochrome action modes and possible multiple pathways for phototropic signal transduction was analyzed based on the experiment results.展开更多
A rice mutant (Oryza sativa L. Nongken 58S) 'photoperiodsensitive male-sterile rice' (PGMR) is sterile under long day-length (LD), but fertile in short days-length (SD). Phytochrome (Phy) has proved to be the ...A rice mutant (Oryza sativa L. Nongken 58S) 'photoperiodsensitive male-sterile rice' (PGMR) is sterile under long day-length (LD), but fertile in short days-length (SD). Phytochrome (Phy) has proved to be the photoreceptor involved in photoperiod-induced male sterile process in PGMR.To speculate how phytochrome functions, PhyA levels in leaf extracts of PGMRand wild-type rice (Oryza sativa L. Nongken 58) under different photoperiods were measured by means of a sandwich enzyme-linked immunosorbent assay (ELISA). The top two leaves of treated rice plants were sampled at the end of the last dark phase for 10 cycles at photoperiod-sensitive stage for fertility alteration in the mutant. Compared with LD treatment, the SD treatment resulted in 39% increase of relative PhyA content (per unit fresh weight) in PGMR, but only in 18% increase in its wild-type. In addition, after 10 cycles of end of far-red irradiations of day,the heading and flowering dates of PGMR were delayed for 2 days, while its male fertility almost remained unchanged. It is well known that the end of day far-red responses are mediated by PhyB.These results suggested that in PGMR PhyA took part in regulation of male sterility, hut PhyB was involved in mediating flowering time.展开更多
The heterotrimeric guanine nucleotide-binding protein （G-protein） has been demonstrated to mediate various signaling pathways in plants. However, its role in phytochrome A （phyA） signaling remains elusive. In this...The heterotrimeric guanine nucleotide-binding protein （G-protein） has been demonstrated to mediate various signaling pathways in plants. However, its role in phytochrome A （phyA） signaling remains elusive. In this study, we discover a new phyA-mediated phenotype designated far-red irradiation （FR） preconditioned cell death, which occurs only in the hypocotyls of FR-grown seedlings following exposure to white light （WL）. The cell death is mitigated in the Gα mutant gpal but aggravated in the Gβ mutant agbl in comparison with the wild type （WT）, indicative of antagonistic roles of GPA1 and AGBI in the phyA-mediated cell-death pathway. Further investigation indicates that FR-induced accumulation of nonphotoconvertible protochlorophyllide （Pchlide^633）, which generates reactive oxygen species （ROS） on exposure to WL, is required for FR-preconditioned cell death. Moreover, ROS is mainly detected in chloroplasts using the fluorescent probe. Interestingly, the application of H2O2 to dark-grown seedlings results in a phenotype similar to FR-preconditioned cell death. This reveals that ROS is a critical mediator for the ceil death. In addition, we observe that agb1 is more sensitive to H2O2 than WT seedlings, indicating that the G-protein may also modify the sensitivity of the seedlings to ROS stress. Taking these results together, we infer that the G-protein may be involved in the phyA signaling pathway to regulate FR-preconditioned cell death ofArabidopsis hypocotyls. A possible mechanism underlying the involvement of the G-protein in phyA signaling is discussed in this study.展开更多
Increasing the planting density of maize is an effective measure to improve its yield.However,plants under high planting density tend to trigger shade avoidance syndrome(SAS),reducing lodging resistance and ultimately...Increasing the planting density of maize is an effective measure to improve its yield.However,plants under high planting density tend to trigger shade avoidance syndrome(SAS),reducing lodging resistance and ultimately yield drop.Phytochrome B(phyB)plays a dominant role in mediating shade avoidance response.This study constructed two hyperactive mutated alleles of maize PHYB1:ZmPHYB1^(Y98F)(mimicking Y104F of AtPHYB)and ZmPHYB1^(Y359F)(mimicking Y361F of AtPHYB).Ectopic expression of ZmPHYB1^(Y98F) and ZmPHYB1^(Y359F) under the control of the ZmPHYB1 promoter in the Arabidopsis phyB-9 background rendered enhanced activity on complementing the phyB-9 related phenotypes compared with ZmPHYB1^(WT).Moreover,similar to the behavior of ZmPHYB1^(WT),ZmPHYB1Y98F and ZmPHYB1^(Y359F) proteins are localized to the nucleus after red light exposure,and could interact with PIF proteins of maize.In addition,expression of ZmPHYB1^(Y98F) and ZmPHYB1^(Y359F) variants under the control of the native ZmPHYB1 promoter attenuated SAS of maize seedlings subjected to simulated shade treatment.It effectively reduced mature maize’s plant height and ear height in field conditions.The results combined demonstrate the utility of ZmPHYB1^(Y98F) and ZmPHYB1^(Y359F) for attenuating SAS and breeding high density-tolerant varieties of maize.展开更多
Soybean(Glycine max)responds to ambient light variation by undergoing multiform morphological alterations,influencing its yield potential and stability in the field.Phytochromes(PHYs)are plant-specific red(R)and far-r...Soybean(Glycine max)responds to ambient light variation by undergoing multiform morphological alterations,influencing its yield potential and stability in the field.Phytochromes(PHYs)are plant-specific red(R)and far-red(FR)light photoreceptors mediating photomorphogenesis and photoperiodic flowering.As an ancient tetraploid,soybean harbors four PHYA,two PHYB,and two PHYE paralogs.Except for GmPHYA2/E4 and GmPHYA3/E3,which have been identified as photoperiod-dependent flowering repressors,the functions of GmPHYs are still largely unclear.We generated a series of individual or combined mutations targeting the GmPHYA or GmPHYB genes using CRISPR/Cas9 technology.Phenotypic analysis revealed that GmPHYB1 mediates predominantly R-light induced photomorphogenesis,whereas GmPHYA2/E4 and GmPHYA3/E3,followed by GmPHYA1 and GmPHYB2,function redundantly and additively in mediating FR light responses in seedling stage.GmPHYA2/E4 and GmPHYA3/E3,with weak influence from GmPHYA1 and GmPHYA4,delay flowering time under natural long-day conditions.This study has demonstrated the diversified functions of GmPHYAs and GmPHYBs in regulating light response,and provides a core set of phytochrome mutant alleles for characterization of their functional mechanisms in regulating agronomic traits of soybean.展开更多
Phytochrome family mainly senses red and far-red light to regulate a range of developmental processes throughout the life cycle of plants. Rice phytochrome gene family is composed of three members known as PHYA, PHYB ...Phytochrome family mainly senses red and far-red light to regulate a range of developmental processes throughout the life cycle of plants. Rice phytochrome gene family is composed of three members known as PHYA, PHYB and PHYC. It has been elucidated that individual phytochromes display both unique and overlapping roles in rice photomorphogenesis by characterization of all rice phytochrome mutants including single mutants, all combinations of double mutants as well as triple mutants. Based on the published data and authors’ ongoing studies, current knowledge of rice phytochrome functions in regulating seedling de-etiolation, root gravitropic response and elongation, plant architecture, flowering time and fertility is summarized. Additionally, the important issues in the field of rice phytochromes are proposed.展开更多
The phytochrome gene family, which is in Arabidopsis thaliana, consists of phytochromes A-E（phyA to phyE）, regulates plant responses to ambient light environments. PhyA and phyB have been characterized in detail, bu...The phytochrome gene family, which is in Arabidopsis thaliana, consists of phytochromes A-E（phyA to phyE）, regulates plant responses to ambient light environments. PhyA and phyB have been characterized in detail, but studies on phyC to phyE have reported discrepant functions. In this study, we show that phyD regulates the Arabidopsis gravitropic response by inhibiting negative gravitropism of hypocotyls under red light condition. PhyD had only a limited effect on the gravitropic response of roots in red light condition. PhyD also enhanced phyB-regulated gravitropic responses in hypocotyls. Moreover, the regulation of hypocotyl gravitropic responses by phyD was dependent upon the red light fluence rate.展开更多
Silencing phytochrome A1 gene (PHYA1) by RNA interference in Upland cotton (Gossypium hirsutum L. cv. Coker 312) had generated PHYA1 RNAi lines with improved fiber quality (longer, stronger and finer fiber). To reveal...Silencing phytochrome A1 gene (PHYA1) by RNA interference in Upland cotton (Gossypium hirsutum L. cv. Coker 312) had generated PHYA1 RNAi lines with improved fiber quality (longer, stronger and finer fiber). To reveal molecular mechanisms that govern fiber development with positive fiber traits, a study of global gene expression profiling of 10-DPA fibers in a PHYA1 RNAi line and its parent Coker 312 was conducted by high-throughput RNA sequencing. A comparative analysis of transcriptomes between the two lines had identified 142 genes that were differentially expressed in the 10-DPA fiber of the RNAi line. Gene Ontology analysis showed that these differentially expressed genes were mainly involved in metabolic pathways, heterocyclic/organic cyclic compound binding and multiple enzyme activities, and cell structures which were reported to play important roles in fiber development. Twenty-eight KEGG pathways were mapped for the 142 genes, and the pathways related to glycolysis/gluconeogenesis and pyruvate metabolism were the most abundant and followed by cytochrome P450-involved pathways, suggesting that fiber improvement could be through the regulation of proteins involved in cytochrome P450 pathways. Genes encoding WRKY transcription factors, sucrose synthase, xyloglucan endotransglucosylase hydrolase, udp-glucuronate: xylan alpha-glucuronosyltransferase, and genes involved in lipid metabolism and ABA/brassinosteroid signal transduction pathways were found differentially expressed in the RNAi line. These genes have direct impacts on cotton fiber quality. The results of this study elucidate molecular signatures and possible mechanisms of fiber improvement in the background of PHYA1 RNAi in cotton and should help for future fine-tuning and programming of cotton fiber development.展开更多
The effects of carbon nanoparticle(CNP)on rice variety Swarna(MTU7029)were investigated.CNP induced effects similar to shade avoidance response(SAR)of Arabidopsis,with increase in shoot length,root length,root number,...The effects of carbon nanoparticle(CNP)on rice variety Swarna(MTU7029)were investigated.CNP induced effects similar to shade avoidance response(SAR)of Arabidopsis,with increase in shoot length,root length,root number,cotyledon area,chlorophyll content and total sugar content in rice seedlings.In mature plants,CNP treatment resulted increase in plant height,number of productive tillers per plant,normalized difference vegetation index,quantum yield and root growth.A total of 320 mg of CNP per plant administered in four doses resulted in improved grain traits such as filled grain rate,100-grain weight,grain length/width ratio,hulling rate,milling rate and head rice recovery.Seeds from the CNP-treated plants showed increase in amylose,starch and soluble sugar contents compared to controls.Strikingly,CNP treatment showed an average of 17.5%increase in yield per plant.Upon investigation to the molecular mechanism behind CNP induction of SAR,a significant downregulation of phytochrome B transcript was found.Decrease in perception of red wavelengths led to responses similar to SAR.Increase in plant’s internal temperature by 0.5ºC±0.1ºC was recorded after CNP treatment.We suggest that the internalized CNP aggregates may serve to absorb extra photons thereby increasing the internal temperature of plants.Phytochrome B accounts the hike in internal temperature and initiates a feed-back reduction of its own transcription.We suggest that moderate SAR is beneficial for rice plants to improve agronomic traits and yield.It presents a potential non-transgenic method for improving rice yield by CNP treatment.展开更多
Phytochromes have been reported to play important roles in seedling de-etiolation and flowering in rice.To identify the roles of phytochromes in regulating root growth and accumulation of dry substances,the lengths of...Phytochromes have been reported to play important roles in seedling de-etiolation and flowering in rice.To identify the roles of phytochromes in regulating root growth and accumulation of dry substances,the lengths of seminal roots and the dry weights of seedlings were measured in the wild type as well as the phytochrome A（phyA） and phytochrome B（phyB） mutants grown under different conditions.When the whole seedlings were exposed to white light,the elongation of the seminal roots was significantly photoinhibited in the wild type,whereas this inhibitory effect was clearly reduced in the phyA and phyB mutants.When the roots of the seedlings were blocked from white light,the phyA and phyB mutants exhibited significantly longer seminal roots than the wild type.These results suggest that both the root-localized and shoot-localized PHYA and PHYB are involved in the photoinhibition of seminal root elongation in rice seedlings.By measuring the dry weights of roots and shoots,it is revealed that PHYB positively regulates the accumulation of dry substances in shoots,however,PHYA exerts the contrary effects on the accumulation of dry substances in roots and shoots of rice seedlings.展开更多
The sequence fragment of PHYA, obtained from transcriptome sequencing,was used as the template, and the full-length c DNA sequence of PHYA gene in tall fescue was amplified using 3＇RACE and 5＇RACE techniques. The c ...The sequence fragment of PHYA, obtained from transcriptome sequencing,was used as the template, and the full-length c DNA sequence of PHYA gene in tall fescue was amplified using 3＇RACE and 5＇RACE techniques. The c DNA sequence of PHYA gene has a complete open reading frame（ORF, 293-6 682 bp）, and it encodes a protein composed of 1 129 amino acids. The N-terminal of Fa PHYA is composed of GAF and Phytochrome domains, and its C-terminal contains two repeated PAS domains, one histidine kinase A domain and one histidine kinase-like ATPase domain. The homology analysis showed that the amino acid sequences of Fa PHYA of tall fescue and PHYAs of gramineous plants have higher homologies（85%）, indicating close genetic relationships. However, the homologies between FaPHYA of tall fescue and PHYAs of monocotyledons are lower, indicating far genetic relationships.展开更多
Separately, it is well-documented that phytochromes (phys), gibberellin (GA) and abscisic acid (ABA) strongly control the seed germination in tomato. However, we hipothesized that phys interact with GA or ABA during t...Separately, it is well-documented that phytochromes (phys), gibberellin (GA) and abscisic acid (ABA) strongly control the seed germination in tomato. However, we hipothesized that phys interact with GA or ABA during this response. Thus, we make an analysis of seed germination of ABA deficient (sit), GA constitutive response (pro), phytochrome deficient (au) mutants as well as, specially, au sit and au pro double mutants of tomato?incubated in the dark or light conditions during 120 h [12 h intervals (i)]. Compared to au, which severely?reduced percentage germination (Gi%) and pro, which did not alter Gi%, au pro showed in the light enhanced Gi% and germination speed index (GSI) besides the reduced average germination time (AGT). Moreover, in the dark, germination of au pro was similar to pro. These results indicate that the mechanisms by which GA modulate germination in tomato are light dependent through the phy signaling, whereas intermediary values of Gi%, GSI and AGT in dark and light of au sit compared to au and sit single mutants indicate an additive effect of the au and sit mutations, suggesting that ABA and phy may act through the parallel signaling pathway.展开更多
Although green light(GL)is located in the middle of the visible light spectrum and regulates a series of plant developmental processes,the mechanism by which it regulates seedling development is largely unknown.In thi...Although green light(GL)is located in the middle of the visible light spectrum and regulates a series of plant developmental processes,the mechanism by which it regulates seedling development is largely unknown.In this study,we demonstrated that GL promotes atypical photomorphogenesis in Arabidopsis thaliana via the dual regulations of phytochrome B(phyB)and phyA.Although the Pr-to-Pfr conversion rates of phyB and phyA under GL were lower than those under red light(RL)in a fluence rate-dependent and time-dependent manner,long-term treatment with GL induced high Pfr/Pr ratios of phyB and phyA.Moreover,GL induced the formation of numerous small phyB photobodies in the nucleus,resulting in atypical photomorphogenesis,with smaller cotyledon opening angles and longer hypocotyls in seedlings compared to RL.The abundance of phyA significantly decreased after short-and long-term GL treatments.We determined that four major PHYTOCHROME-INTERACTING FACTORs(PIFs:PIF1,PIF3,PIF4,and PIF5)act downstream of phyB in GL-mediated cotyledon opening.In addition,GL plays opposite roles in regulating different PIFs.For example,under continuous GL,the protein levels of all PIFs decreased,whereas the transcript levels of PIF4 and PIF5 strongly increased compared with dark treatment.Taken together,our work provides a detailed molecular framework for understanding the role of the antagonistic regulations of phyB and phyA in GL-mediated atypical photomorphogenesis.展开更多
Over the past few decades,significant improvements in maize yield have been largely attributed to increased plant density of upright hybrid varieties rather than increased yield per plant.However,dense planting trigge...Over the past few decades,significant improvements in maize yield have been largely attributed to increased plant density of upright hybrid varieties rather than increased yield per plant.However,dense planting triggers shade avoidance responses(SARs)that optimize light absorption but impair plant vigor and performance,limiting yield improvement through increasing plant density.In this study,we demonstrated that high-density-induced leaf angle narrowing and stem/stalk elongation are largely dependent on phytochrome B(phyB1/B2),the primaryphotoreceptor responsible for perceiving red(R)and far-red(FR)light in maize.We found that maize phyB physically interacts with the LIGULELESS1(LG1),a classical key regulator of leaf angle,to coordinately regulate plant architecture and density tolerance.The abundance of LG1 is significantly increased by phyB under high R:FR light(low density)but rapidly decreases under low R:FR light(high density),correlating with variations in leaf angle and plant height under various densities.In addition,we identified the homeobox transcription factor HB53 as a target co-repressed by both phyB and LG1 but rapidly induced by canopy shade.Genetic and cellular analyses showed that HB53 regulates plant architecture by controlling the elongation and division of ligular adaxial and abaxial cells.Taken together,these findings uncover the phyB-LG1-HB53 regulatory module as a key molecular mechanism governing plant architecture and density tolerance,providing potential genetic targets for breeding maize hybrid varieties suitable for high-density planting.展开更多
In Arabidopsis,although studies have demonstrated that phytochrome A(phyA)and phyB are involved in blue light signaling,how blue light-activated phytochromes modulate the activity of the CONSTITUTIVELY PHOTOMORPHOGENI...In Arabidopsis,although studies have demonstrated that phytochrome A(phyA)and phyB are involved in blue light signaling,how blue light-activated phytochromes modulate the activity of the CONSTITUTIVELY PHOTOMORPHOGENIC1(COP1)-SUPPRESSOR OF PHYA-105(SPA1)E3 complex remains largely unknown.Here,we show that phyA responds to early and weak blue light,whereas phyB responds to sustainable and strong blue light.Activation of both phyA and phyB by blue light inhibits SPA1 activity.Specifically,blue light irradiation promoted the nuclear import of both phytochromes to stimulate their binding to SPA1,abolishing SPA1’s interaction with LONG HYPOCOTYL 5(HY5)to release HY5,which promoted seedling photomorphogenesis.展开更多
In Arabidopsis seeds, germination is promoted only by phytochromes, principally phytochrome B （phyB） and phytochrome A （phyA）. Despite the abundant information concerning the molecular basis of phyB signaling down...In Arabidopsis seeds, germination is promoted only by phytochromes, principally phytochrome B （phyB） and phytochrome A （phyA）. Despite the abundant information concerning the molecular basis of phyB signaling downstream of PIF1/PIL5, the signaling network inducing germination by phyA is poorly known. Here, we describe the influence of phyA on the transcriptome of Arabidopsis seeds when germination is induced by a far-red （FR） pulse. The expression of 11% of the genome was significantly regulated by phyA. Most of the genes were up-regulated and the changes noted late （i.e. 5 h after a FR pulse）, whereas changes in down-regulated genes were more abundant earlier （i.e. 0.5 h after a FR pulse）. Auxin- and GA-associated elements were overrepresented in the genes that were modified by phyA. A significant number of genes whose expression was affected by phyA had not been previously reported to be dependent on PIL5. Among them, homozygotic mutant seeds of MYB66, a SAUR-like protein, PIN7, and GASA4 showed an impaired promo- tion of germination by phyA. Natural variation at the transcriptional level was found in early signaling and GA metabolic genes, but not in ABA metabolic and expansin genes between Columbia and Landsberg erecta accessions. Although phyA and phyB/PIL5 signaling pathways share some molecular components, our data suggest that phyA signaling is partially independent of PIL5 when germination is promoted by very low fluences of light.展开更多
Old leaves of wild-type rice plants （Oryza sativa L. cv. Nipponbare） are more resistant to blast fungus （Magnaporthe grisea） than new leaves. In contrast, both old and new leaves of the rice phytochrome triple mut...Old leaves of wild-type rice plants （Oryza sativa L. cv. Nipponbare） are more resistant to blast fungus （Magnaporthe grisea） than new leaves. In contrast, both old and new leaves of the rice phytochrome triple mutant （phyAphyBphyC） are susceptible to blast fungus. We demonstrate that pathogenesis-related class 1 （PR1） proteins are rapidly and strongly induced during M. grisea infection and following exogenous jasmonate （JA） or salicylic acid （SA） exposure in the old leaves, but not in the new leaves of the wild-type. In contrast, the accumulation of PR1 proteins was significantly attenuated in old and new leaves of the phyAphyBphyC mutant. These results suggest that phytochromes are required for the induction of PR1 proteins in rice. Basal transcription levels of PRla and PRlb were substantially higher in the wildtype as compared to the phyAphyBphyC mutant, suggesting that phytochromes also are required for basal expression of PR1 genes. Moreover, the transcript levels of genes known to function in SA- or JA-dependent defense pathways were regulated by leaf age and functional phytochromes. Taken together, our findings demonstrate that phytochromes are required in rice for age-related resistance to M. grisea and may indirectly increase PR1 gene expression by regulating SA- and JA-dependent defense pathways.展开更多
Seedling development including hypocotyl elongation is a critical phase in the plant life cycle. Light regula- tion of hypocotyl elongation is primarily mediated through the blue light photoreceptor cryptochrome and r...Seedling development including hypocotyl elongation is a critical phase in the plant life cycle. Light regula- tion of hypocotyl elongation is primarily mediated through the blue light photoreceptor cryptochrome and red/far-red light photoreceptor phytochrome signaling pathways, comprising regulators including COP1, HY5, and phytochrome- interacting factors （PIFs）. The novel phytohormones, strigolactones, also participate in regulating hypocotyl growth. However, how strigolactone coordinates with light and photoreceptors in the regulation of hypocotyl elongation is largely unclear. Here, we demonstrate that strigolactone inhibition of hypocotyl elongation is dependent on cryp- tochrome and phytochrome signaling pathways. The photoreceptor mutants cry1 cry2, phyA, and phyB are hyposensi- tive to strigolactone analog GR24 under the respective monochromatic light conditions, while cop1 and pifl pif3 pif4 pif5 （pifq） quadruple mutants are hypersensitive to GR24 in darkness. Genetic studies indicate that the enhanced respon- siveness of cop1 to GR24 is dependent on HY5 and MAX2, while that of pifq is independent of HY5. Further studies demonstrate that GR24 constitutively up-regulates HY5 expression in the dark and light, whereas GR24-promoted HY5 protein accumulation is light- and cryptochrome and phytochrome photoreceptor-dependent. These results suggest that the light dependency of strigolactone regulation of hypocotyl elongation is likely mediated through MAX2-dependent promotion of HY5 expression, light-dependent accumulation of HY5, and PIF-regulated components.展开更多
Phytochrome B (phyB), the primary red light photoreceptor, promotes photomorphogenesis in Arabidopsis by interacting with the basic helix-loop-helix transcriptional factor PIF3 and inducing its phosphorylation and deg...Phytochrome B (phyB), the primary red light photoreceptor, promotes photomorphogenesis in Arabidopsis by interacting with the basic helix-loop-helix transcriptional factor PIF3 and inducing its phosphorylation and degradation. Heterotrimeric G proteins are known to regulate various developmental processes in plants and animals. In Arabidopsis, the G-protein β subunit AGB1 is known to repress photomorphogenesis. However, whether and how phyB and AGB1 coordinately regulate photomorphogenesis are largely unknown. Here we show that phyB physically interacts with AGB1 in a red light-dependent manner and that AGB1 interacts directly with PIF3. Moreover, we demonstrate that the AGB1-PIF3 interaction inhibits the association of PIF3 with phyB, leading to reduced phosphorylation and degradation of PIF3, whereas the phyB-AGB1 interaction represses the association of PIF3 with AGB1, resulting in enhaneed phosphorylation and degradation of PIF3. Our results suggest that phyB and AGB1 antagonistically regulate PIF3 stability by dynamically interacting with each other and PIF3. This dynamic mechanism may allow plants to balanee phyB and G-protein signaling to optimize photomorphogenesis.展开更多
Identification of all genes involved in the phytochrome （phy）-medieted responses of plants to their light environment is an important goal in providing an overall understanding of light-regulated growth end developm...Identification of all genes involved in the phytochrome （phy）-medieted responses of plants to their light environment is an important goal in providing an overall understanding of light-regulated growth end development. This article highlights end integrates the central findings of two recent comprehensive studies in Arabidopsis that have identified the genome-wide set of phy-reguleted genes that respond rapidly to red-light signals upon first exposure of dark-grown seedlings, and have tested the functional relevance to normal seedling photomorphogenesis of an Initial subset of these genes. The data： （a） reveal considerable complexity in the channeling of the light signals through the different phy-femily members （phyA to phyE） to responsive genes; （b） identify a diversity of transcription-factor-encoding genes as major early, if not primary, targets of phy signaling, end, therefore, as potentially important regulators in the transcriptional-network hierarchy; and （c） identify auxin-related genes as the dominant class among rapidly-regulated, hormone-related genes. However, reverse-genetic functional profiling of a selected subset of these genes reveals that only a limited fraction are necessary for optimal phy-induced seedling deetioletion.展开更多
文摘Previous studies have examined the effects of red light (R) on phototropism of maize ( Zea mays L. cv. Royaldent Hit 85) coleoptiles. The R effect on time-dependent phototropism (TDP) was further studied by characterizing its fluence-response relationship. The results showed the R effect was a low-fluence-response, unlike those on pulse-induced phototropisms that show a very-low-fluence-response mode. A subsequent pulse of far-red light (FR) could reverse the R effect. TDP responsiveness, however, recovered as the following FR was extended, The FR-dependent increase in TDP responsiveness was obtained even coleoptiles were pretreated only with FR. It suggested that TDP responsiveness could also be established in response to a FR signal. The fluence-response relationship for the effect of FR was then investigated. The effect of FR depended on the time of irradiation and required high photon fluences. Because reciprocity was invalid at the higher fluence range, the effect of FR would be a high-irradiance-response mode. Relation between phytochrome action modes and possible multiple pathways for phototropic signal transduction was analyzed based on the experiment results.
文摘A rice mutant (Oryza sativa L. Nongken 58S) 'photoperiodsensitive male-sterile rice' (PGMR) is sterile under long day-length (LD), but fertile in short days-length (SD). Phytochrome (Phy) has proved to be the photoreceptor involved in photoperiod-induced male sterile process in PGMR.To speculate how phytochrome functions, PhyA levels in leaf extracts of PGMRand wild-type rice (Oryza sativa L. Nongken 58) under different photoperiods were measured by means of a sandwich enzyme-linked immunosorbent assay (ELISA). The top two leaves of treated rice plants were sampled at the end of the last dark phase for 10 cycles at photoperiod-sensitive stage for fertility alteration in the mutant. Compared with LD treatment, the SD treatment resulted in 39% increase of relative PhyA content (per unit fresh weight) in PGMR, but only in 18% increase in its wild-type. In addition, after 10 cycles of end of far-red irradiations of day,the heading and flowering dates of PGMR were delayed for 2 days, while its male fertility almost remained unchanged. It is well known that the end of day far-red responses are mediated by PhyB.These results suggested that in PGMR PhyA took part in regulation of male sterility, hut PhyB was involved in mediating flowering time.
文摘The heterotrimeric guanine nucleotide-binding protein （G-protein） has been demonstrated to mediate various signaling pathways in plants. However, its role in phytochrome A （phyA） signaling remains elusive. In this study, we discover a new phyA-mediated phenotype designated far-red irradiation （FR） preconditioned cell death, which occurs only in the hypocotyls of FR-grown seedlings following exposure to white light （WL）. The cell death is mitigated in the Gα mutant gpal but aggravated in the Gβ mutant agbl in comparison with the wild type （WT）, indicative of antagonistic roles of GPA1 and AGBI in the phyA-mediated cell-death pathway. Further investigation indicates that FR-induced accumulation of nonphotoconvertible protochlorophyllide （Pchlide^633）, which generates reactive oxygen species （ROS） on exposure to WL, is required for FR-preconditioned cell death. Moreover, ROS is mainly detected in chloroplasts using the fluorescent probe. Interestingly, the application of H2O2 to dark-grown seedlings results in a phenotype similar to FR-preconditioned cell death. This reveals that ROS is a critical mediator for the ceil death. In addition, we observe that agb1 is more sensitive to H2O2 than WT seedlings, indicating that the G-protein may also modify the sensitivity of the seedlings to ROS stress. Taking these results together, we infer that the G-protein may be involved in the phyA signaling pathway to regulate FR-preconditioned cell death ofArabidopsis hypocotyls. A possible mechanism underlying the involvement of the G-protein in phyA signaling is discussed in this study.
基金financially supported by the Major Program of Guangdong Basic and Applied Research,China(2019B030302006)the National Natural Science Foundation of China(31801377)the funding from the State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources,China(SKLCUSA-b201801)。
文摘Increasing the planting density of maize is an effective measure to improve its yield.However,plants under high planting density tend to trigger shade avoidance syndrome(SAS),reducing lodging resistance and ultimately yield drop.Phytochrome B(phyB)plays a dominant role in mediating shade avoidance response.This study constructed two hyperactive mutated alleles of maize PHYB1:ZmPHYB1^(Y98F)(mimicking Y104F of AtPHYB)and ZmPHYB1^(Y359F)(mimicking Y361F of AtPHYB).Ectopic expression of ZmPHYB1^(Y98F) and ZmPHYB1^(Y359F) under the control of the ZmPHYB1 promoter in the Arabidopsis phyB-9 background rendered enhanced activity on complementing the phyB-9 related phenotypes compared with ZmPHYB1^(WT).Moreover,similar to the behavior of ZmPHYB1^(WT),ZmPHYB1Y98F and ZmPHYB1^(Y359F) proteins are localized to the nucleus after red light exposure,and could interact with PIF proteins of maize.In addition,expression of ZmPHYB1^(Y98F) and ZmPHYB1^(Y359F) variants under the control of the native ZmPHYB1 promoter attenuated SAS of maize seedlings subjected to simulated shade treatment.It effectively reduced mature maize’s plant height and ear height in field conditions.The results combined demonstrate the utility of ZmPHYB1^(Y98F) and ZmPHYB1^(Y359F) for attenuating SAS and breeding high density-tolerant varieties of maize.
基金supported by the National Natural Science Foundation of China(31871705,32072091)the Agricultural Science and Technology Innovation Program(ASTIP)of the Chinese Academy of Agricultural Sciencesthe Central Public-interest Scientific Institution Basal Research Fund。
文摘Soybean(Glycine max)responds to ambient light variation by undergoing multiform morphological alterations,influencing its yield potential and stability in the field.Phytochromes(PHYs)are plant-specific red(R)and far-red(FR)light photoreceptors mediating photomorphogenesis and photoperiodic flowering.As an ancient tetraploid,soybean harbors four PHYA,two PHYB,and two PHYE paralogs.Except for GmPHYA2/E4 and GmPHYA3/E3,which have been identified as photoperiod-dependent flowering repressors,the functions of GmPHYs are still largely unclear.We generated a series of individual or combined mutations targeting the GmPHYA or GmPHYB genes using CRISPR/Cas9 technology.Phenotypic analysis revealed that GmPHYB1 mediates predominantly R-light induced photomorphogenesis,whereas GmPHYA2/E4 and GmPHYA3/E3,followed by GmPHYA1 and GmPHYB2,function redundantly and additively in mediating FR light responses in seedling stage.GmPHYA2/E4 and GmPHYA3/E3,with weak influence from GmPHYA1 and GmPHYA4,delay flowering time under natural long-day conditions.This study has demonstrated the diversified functions of GmPHYAs and GmPHYBs in regulating light response,and provides a core set of phytochrome mutant alleles for characterization of their functional mechanisms in regulating agronomic traits of soybean.
基金supported by the grants from the Chinese National Natural Science Foundations (Grant Nos. 30870192 and 30971744)the National Major Science and Technology Project to Create New Crop Varieties Using Gene Transfer Technical (Grant No. 2009ZX08001-029B)the Open Research Program from the Key Laboratory of Crop Biology, China (Grant No. 2009KF04)
文摘Phytochrome family mainly senses red and far-red light to regulate a range of developmental processes throughout the life cycle of plants. Rice phytochrome gene family is composed of three members known as PHYA, PHYB and PHYC. It has been elucidated that individual phytochromes display both unique and overlapping roles in rice photomorphogenesis by characterization of all rice phytochrome mutants including single mutants, all combinations of double mutants as well as triple mutants. Based on the published data and authors’ ongoing studies, current knowledge of rice phytochrome functions in regulating seedling de-etiolation, root gravitropic response and elongation, plant architecture, flowering time and fertility is summarized. Additionally, the important issues in the field of rice phytochromes are proposed.
基金supported by funds from the Genetically Modified Organisms Breeding Major Projects of China (2011ZX08010-002)the National Natural Science Foundation of China (30871438 and 31170267)the Natural Science Foundation of Xinjiang, China (2012211B49)
文摘The phytochrome gene family, which is in Arabidopsis thaliana, consists of phytochromes A-E（phyA to phyE）, regulates plant responses to ambient light environments. PhyA and phyB have been characterized in detail, but studies on phyC to phyE have reported discrepant functions. In this study, we show that phyD regulates the Arabidopsis gravitropic response by inhibiting negative gravitropism of hypocotyls under red light condition. PhyD had only a limited effect on the gravitropic response of roots in red light condition. PhyD also enhanced phyB-regulated gravitropic responses in hypocotyls. Moreover, the regulation of hypocotyl gravitropic responses by phyD was dependent upon the red light fluence rate.
文摘Silencing phytochrome A1 gene (PHYA1) by RNA interference in Upland cotton (Gossypium hirsutum L. cv. Coker 312) had generated PHYA1 RNAi lines with improved fiber quality (longer, stronger and finer fiber). To reveal molecular mechanisms that govern fiber development with positive fiber traits, a study of global gene expression profiling of 10-DPA fibers in a PHYA1 RNAi line and its parent Coker 312 was conducted by high-throughput RNA sequencing. A comparative analysis of transcriptomes between the two lines had identified 142 genes that were differentially expressed in the 10-DPA fiber of the RNAi line. Gene Ontology analysis showed that these differentially expressed genes were mainly involved in metabolic pathways, heterocyclic/organic cyclic compound binding and multiple enzyme activities, and cell structures which were reported to play important roles in fiber development. Twenty-eight KEGG pathways were mapped for the 142 genes, and the pathways related to glycolysis/gluconeogenesis and pyruvate metabolism were the most abundant and followed by cytochrome P450-involved pathways, suggesting that fiber improvement could be through the regulation of proteins involved in cytochrome P450 pathways. Genes encoding WRKY transcription factors, sucrose synthase, xyloglucan endotransglucosylase hydrolase, udp-glucuronate: xylan alpha-glucuronosyltransferase, and genes involved in lipid metabolism and ABA/brassinosteroid signal transduction pathways were found differentially expressed in the RNAi line. These genes have direct impacts on cotton fiber quality. The results of this study elucidate molecular signatures and possible mechanisms of fiber improvement in the background of PHYA1 RNAi in cotton and should help for future fine-tuning and programming of cotton fiber development.
基金supported by the Department of Science and Technology,Women Scientist Scheme-A in India(Grant No.SR/WOS-A/LS-369/2018)Science Engineering Research Board,Young Scientist Start-Up Grant in India(Grant No.YSS-2015-000659)+1 种基金Department of Science and Technology,Science Engineering Research Board,India(Grant No.EMR/2014/000533)Department of Atomic Energy,National Institute of Science Education and Research in India.
文摘The effects of carbon nanoparticle(CNP)on rice variety Swarna(MTU7029)were investigated.CNP induced effects similar to shade avoidance response(SAR)of Arabidopsis,with increase in shoot length,root length,root number,cotyledon area,chlorophyll content and total sugar content in rice seedlings.In mature plants,CNP treatment resulted increase in plant height,number of productive tillers per plant,normalized difference vegetation index,quantum yield and root growth.A total of 320 mg of CNP per plant administered in four doses resulted in improved grain traits such as filled grain rate,100-grain weight,grain length/width ratio,hulling rate,milling rate and head rice recovery.Seeds from the CNP-treated plants showed increase in amylose,starch and soluble sugar contents compared to controls.Strikingly,CNP treatment showed an average of 17.5%increase in yield per plant.Upon investigation to the molecular mechanism behind CNP induction of SAR,a significant downregulation of phytochrome B transcript was found.Decrease in perception of red wavelengths led to responses similar to SAR.Increase in plant’s internal temperature by 0.5ºC±0.1ºC was recorded after CNP treatment.We suggest that the internalized CNP aggregates may serve to absorb extra photons thereby increasing the internal temperature of plants.Phytochrome B accounts the hike in internal temperature and initiates a feed-back reduction of its own transcription.We suggest that moderate SAR is beneficial for rice plants to improve agronomic traits and yield.It presents a potential non-transgenic method for improving rice yield by CNP treatment.
基金supported by grants from the Shandong Natural Science Funds for Distinguished Young Scholar,China (Grant No. JQ200911)the Chinese National Natural Science Foundation (GrantNo. 30971744)the Chinese Ministry of Agriculture(Grant No. 2009ZX08001-029B)
文摘Phytochromes have been reported to play important roles in seedling de-etiolation and flowering in rice.To identify the roles of phytochromes in regulating root growth and accumulation of dry substances,the lengths of seminal roots and the dry weights of seedlings were measured in the wild type as well as the phytochrome A（phyA） and phytochrome B（phyB） mutants grown under different conditions.When the whole seedlings were exposed to white light,the elongation of the seminal roots was significantly photoinhibited in the wild type,whereas this inhibitory effect was clearly reduced in the phyA and phyB mutants.When the roots of the seedlings were blocked from white light,the phyA and phyB mutants exhibited significantly longer seminal roots than the wild type.These results suggest that both the root-localized and shoot-localized PHYA and PHYB are involved in the photoinhibition of seminal root elongation in rice seedlings.By measuring the dry weights of roots and shoots,it is revealed that PHYB positively regulates the accumulation of dry substances in shoots,however,PHYA exerts the contrary effects on the accumulation of dry substances in roots and shoots of rice seedlings.
基金Supported by National Natural Science Foundation of China(31360576)~~
文摘The sequence fragment of PHYA, obtained from transcriptome sequencing,was used as the template, and the full-length c DNA sequence of PHYA gene in tall fescue was amplified using 3＇RACE and 5＇RACE techniques. The c DNA sequence of PHYA gene has a complete open reading frame（ORF, 293-6 682 bp）, and it encodes a protein composed of 1 129 amino acids. The N-terminal of Fa PHYA is composed of GAF and Phytochrome domains, and its C-terminal contains two repeated PAS domains, one histidine kinase A domain and one histidine kinase-like ATPase domain. The homology analysis showed that the amino acid sequences of Fa PHYA of tall fescue and PHYAs of gramineous plants have higher homologies（85%）, indicating close genetic relationships. However, the homologies between FaPHYA of tall fescue and PHYAs of monocotyledons are lower, indicating far genetic relationships.
文摘Separately, it is well-documented that phytochromes (phys), gibberellin (GA) and abscisic acid (ABA) strongly control the seed germination in tomato. However, we hipothesized that phys interact with GA or ABA during this response. Thus, we make an analysis of seed germination of ABA deficient (sit), GA constitutive response (pro), phytochrome deficient (au) mutants as well as, specially, au sit and au pro double mutants of tomato?incubated in the dark or light conditions during 120 h [12 h intervals (i)]. Compared to au, which severely?reduced percentage germination (Gi%) and pro, which did not alter Gi%, au pro showed in the light enhanced Gi% and germination speed index (GSI) besides the reduced average germination time (AGT). Moreover, in the dark, germination of au pro was similar to pro. These results indicate that the mechanisms by which GA modulate germination in tomato are light dependent through the phy signaling, whereas intermediary values of Gi%, GSI and AGT in dark and light of au sit compared to au and sit single mutants indicate an additive effect of the au and sit mutations, suggesting that ABA and phy may act through the parallel signaling pathway.
基金supported by the Excellent Young Talents Fund Program of Higher Education Institutions of Anhui Province(2023AH030049)Anhui Agricultural University Startup Fund(grant no.rc422115,to J.J.L.)Anhui Province Fund for University Development(22103103)。
文摘Although green light(GL)is located in the middle of the visible light spectrum and regulates a series of plant developmental processes,the mechanism by which it regulates seedling development is largely unknown.In this study,we demonstrated that GL promotes atypical photomorphogenesis in Arabidopsis thaliana via the dual regulations of phytochrome B(phyB)and phyA.Although the Pr-to-Pfr conversion rates of phyB and phyA under GL were lower than those under red light(RL)in a fluence rate-dependent and time-dependent manner,long-term treatment with GL induced high Pfr/Pr ratios of phyB and phyA.Moreover,GL induced the formation of numerous small phyB photobodies in the nucleus,resulting in atypical photomorphogenesis,with smaller cotyledon opening angles and longer hypocotyls in seedlings compared to RL.The abundance of phyA significantly decreased after short-and long-term GL treatments.We determined that four major PHYTOCHROME-INTERACTING FACTORs(PIFs:PIF1,PIF3,PIF4,and PIF5)act downstream of phyB in GL-mediated cotyledon opening.In addition,GL plays opposite roles in regulating different PIFs.For example,under continuous GL,the protein levels of all PIFs decreased,whereas the transcript levels of PIF4 and PIF5 strongly increased compared with dark treatment.Taken together,our work provides a detailed molecular framework for understanding the role of the antagonistic regulations of phyB and phyA in GL-mediated atypical photomorphogenesis.
基金the National Natural Science Foundation of China(32270263 to G.L.,32130077 to H.W.,and 32272140 to P.L.)the Shandong Provincial Natural Science Foundation(ZR2022QC095,ZR2020MC023,ZR2022MC019).
文摘Over the past few decades,significant improvements in maize yield have been largely attributed to increased plant density of upright hybrid varieties rather than increased yield per plant.However,dense planting triggers shade avoidance responses(SARs)that optimize light absorption but impair plant vigor and performance,limiting yield improvement through increasing plant density.In this study,we demonstrated that high-density-induced leaf angle narrowing and stem/stalk elongation are largely dependent on phytochrome B(phyB1/B2),the primaryphotoreceptor responsible for perceiving red(R)and far-red(FR)light in maize.We found that maize phyB physically interacts with the LIGULELESS1(LG1),a classical key regulator of leaf angle,to coordinately regulate plant architecture and density tolerance.The abundance of LG1 is significantly increased by phyB under high R:FR light(low density)but rapidly decreases under low R:FR light(high density),correlating with variations in leaf angle and plant height under various densities.In addition,we identified the homeobox transcription factor HB53 as a target co-repressed by both phyB and LG1 but rapidly induced by canopy shade.Genetic and cellular analyses showed that HB53 regulates plant architecture by controlling the elongation and division of ligular adaxial and abaxial cells.Taken together,these findings uncover the phyB-LG1-HB53 regulatory module as a key molecular mechanism governing plant architecture and density tolerance,providing potential genetic targets for breeding maize hybrid varieties suitable for high-density planting.
基金supported by funds from the National Natural Science Foundation of China 31871709,31570268,31400259,and 31170267。
文摘In Arabidopsis,although studies have demonstrated that phytochrome A(phyA)and phyB are involved in blue light signaling,how blue light-activated phytochromes modulate the activity of the CONSTITUTIVELY PHOTOMORPHOGENIC1(COP1)-SUPPRESSOR OF PHYA-105(SPA1)E3 complex remains largely unknown.Here,we show that phyA responds to early and weak blue light,whereas phyB responds to sustainable and strong blue light.Activation of both phyA and phyB by blue light inhibits SPA1 activity.Specifically,blue light irradiation promoted the nuclear import of both phytochromes to stimulate their binding to SPA1,abolishing SPA1’s interaction with LONG HYPOCOTYL 5(HY5)to release HY5,which promoted seedling photomorphogenesis.
文摘In Arabidopsis seeds, germination is promoted only by phytochromes, principally phytochrome B （phyB） and phytochrome A （phyA）. Despite the abundant information concerning the molecular basis of phyB signaling downstream of PIF1/PIL5, the signaling network inducing germination by phyA is poorly known. Here, we describe the influence of phyA on the transcriptome of Arabidopsis seeds when germination is induced by a far-red （FR） pulse. The expression of 11% of the genome was significantly regulated by phyA. Most of the genes were up-regulated and the changes noted late （i.e. 5 h after a FR pulse）, whereas changes in down-regulated genes were more abundant earlier （i.e. 0.5 h after a FR pulse）. Auxin- and GA-associated elements were overrepresented in the genes that were modified by phyA. A significant number of genes whose expression was affected by phyA had not been previously reported to be dependent on PIL5. Among them, homozygotic mutant seeds of MYB66, a SAUR-like protein, PIN7, and GASA4 showed an impaired promo- tion of germination by phyA. Natural variation at the transcriptional level was found in early signaling and GA metabolic genes, but not in ABA metabolic and expansin genes between Columbia and Landsberg erecta accessions. Although phyA and phyB/PIL5 signaling pathways share some molecular components, our data suggest that phyA signaling is partially independent of PIL5 when germination is promoted by very low fluences of light.
文摘Old leaves of wild-type rice plants （Oryza sativa L. cv. Nipponbare） are more resistant to blast fungus （Magnaporthe grisea） than new leaves. In contrast, both old and new leaves of the rice phytochrome triple mutant （phyAphyBphyC） are susceptible to blast fungus. We demonstrate that pathogenesis-related class 1 （PR1） proteins are rapidly and strongly induced during M. grisea infection and following exogenous jasmonate （JA） or salicylic acid （SA） exposure in the old leaves, but not in the new leaves of the wild-type. In contrast, the accumulation of PR1 proteins was significantly attenuated in old and new leaves of the phyAphyBphyC mutant. These results suggest that phytochromes are required for the induction of PR1 proteins in rice. Basal transcription levels of PRla and PRlb were substantially higher in the wildtype as compared to the phyAphyBphyC mutant, suggesting that phytochromes also are required for basal expression of PR1 genes. Moreover, the transcript levels of genes known to function in SA- or JA-dependent defense pathways were regulated by leaf age and functional phytochromes. Taken together, our findings demonstrate that phytochromes are required in rice for age-related resistance to M. grisea and may indirectly increase PR1 gene expression by regulating SA- and JA-dependent defense pathways.
基金grants from the National Natural Science Foundation of China，the National Special Grant for Transgenic Crops，the Science and Technology Commission of the Shanghai Municipality，the Shanghai Leading Academic Discipline Project
文摘Seedling development including hypocotyl elongation is a critical phase in the plant life cycle. Light regula- tion of hypocotyl elongation is primarily mediated through the blue light photoreceptor cryptochrome and red/far-red light photoreceptor phytochrome signaling pathways, comprising regulators including COP1, HY5, and phytochrome- interacting factors （PIFs）. The novel phytohormones, strigolactones, also participate in regulating hypocotyl growth. However, how strigolactone coordinates with light and photoreceptors in the regulation of hypocotyl elongation is largely unclear. Here, we demonstrate that strigolactone inhibition of hypocotyl elongation is dependent on cryp- tochrome and phytochrome signaling pathways. The photoreceptor mutants cry1 cry2, phyA, and phyB are hyposensi- tive to strigolactone analog GR24 under the respective monochromatic light conditions, while cop1 and pifl pif3 pif4 pif5 （pifq） quadruple mutants are hypersensitive to GR24 in darkness. Genetic studies indicate that the enhanced respon- siveness of cop1 to GR24 is dependent on HY5 and MAX2, while that of pifq is independent of HY5. Further studies demonstrate that GR24 constitutively up-regulates HY5 expression in the dark and light, whereas GR24-promoted HY5 protein accumulation is light- and cryptochrome and phytochrome photoreceptor-dependent. These results suggest that the light dependency of strigolactone regulation of hypocotyl elongation is likely mediated through MAX2-dependent promotion of HY5 expression, light-dependent accumulation of HY5, and PIF-regulated components.
基金The National Natural Science Foundation of China grants to H.-Q.Y.(31530085) and H.L.L (31570282 and 31170266)The National Key Research and Development Program of China grant (2017YFA0503802)the Science and Technology Commission of Shanghai Municipality grant (18DZ2260500).
文摘Phytochrome B (phyB), the primary red light photoreceptor, promotes photomorphogenesis in Arabidopsis by interacting with the basic helix-loop-helix transcriptional factor PIF3 and inducing its phosphorylation and degradation. Heterotrimeric G proteins are known to regulate various developmental processes in plants and animals. In Arabidopsis, the G-protein β subunit AGB1 is known to repress photomorphogenesis. However, whether and how phyB and AGB1 coordinately regulate photomorphogenesis are largely unknown. Here we show that phyB physically interacts with AGB1 in a red light-dependent manner and that AGB1 interacts directly with PIF3. Moreover, we demonstrate that the AGB1-PIF3 interaction inhibits the association of PIF3 with phyB, leading to reduced phosphorylation and degradation of PIF3, whereas the phyB-AGB1 interaction represses the association of PIF3 with AGB1, resulting in enhaneed phosphorylation and degradation of PIF3. Our results suggest that phyB and AGB1 antagonistically regulate PIF3 stability by dynamically interacting with each other and PIF3. This dynamic mechanism may allow plants to balanee phyB and G-protein signaling to optimize photomorphogenesis.
基金Supported by National Institute of Health Grant GM47475, Department of Energy Grant DE-FG03-87ER13742, and U.S. Department of Agriculture Grant 5335-21000-010-00D. Publication of this paper is supported by the National Natural Science Foundation of China （30624808） and Science Publication Foundation of the Chinese Academy of Sciences.Acknowledgements Thank the coauthors of the original research publications used as the basis for this article, and Jim Tepperman for figure preparation and help with the manuscript.
文摘Identification of all genes involved in the phytochrome （phy）-medieted responses of plants to their light environment is an important goal in providing an overall understanding of light-regulated growth end development. This article highlights end integrates the central findings of two recent comprehensive studies in Arabidopsis that have identified the genome-wide set of phy-reguleted genes that respond rapidly to red-light signals upon first exposure of dark-grown seedlings, and have tested the functional relevance to normal seedling photomorphogenesis of an Initial subset of these genes. The data： （a） reveal considerable complexity in the channeling of the light signals through the different phy-femily members （phyA to phyE） to responsive genes; （b） identify a diversity of transcription-factor-encoding genes as major early, if not primary, targets of phy signaling, end, therefore, as potentially important regulators in the transcriptional-network hierarchy; and （c） identify auxin-related genes as the dominant class among rapidly-regulated, hormone-related genes. However, reverse-genetic functional profiling of a selected subset of these genes reveals that only a limited fraction are necessary for optimal phy-induced seedling deetioletion.
