A new C-glycosylflavone, named panzhihuacycaside (1), was isolated from the leaves of Cycas panzhihuaensis L. Zhou et S. Y. Yang (Cycadaceae) along with 2,3-dihydrohinokiflavone (2), 5,5',7,7', 4',4'&#...A new C-glycosylflavone, named panzhihuacycaside (1), was isolated from the leaves of Cycas panzhihuaensis L. Zhou et S. Y. Yang (Cycadaceae) along with 2,3-dihydrohinokiflavone (2), 5,5',7,7', 4',4''-hexahydroxy-(2',8')-biflavone (3), vanillic acid (4), P-sitosterol (5) and daucosterol (6). Their structures were elucidated by spectral and chemical evidence.展开更多
Cycas panzhihuaensis L.Zhou & S.Y.Yang(Cycadaceae) is an endangered gymnosperm species endemic to the dry-hot valley of the Jinsha River basin in southwest China.Although the wild C.panzhihuaensis population from ...Cycas panzhihuaensis L.Zhou & S.Y.Yang(Cycadaceae) is an endangered gymnosperm species endemic to the dry-hot valley of the Jinsha River basin in southwest China.Although the wild C.panzhihuaensis population from Panzhihua Cycad Natural Reserve is well protected and its genetic diversity has been well assessed,the genetic characteristics of populations outside the nature reserve,which face larger risks of extinction,remain unknown.Furthermore,the population genetics and historical dynamics of this endemic and endangered species have not been examined across its entire range.In this study,to analyze the genetic diversity,phylogeographical structure and demographic history of C.panzhihuaensis from all its seven known locations,we sequenced and compared molecular data from chloroplastic DNA(psbA-trnH,psbM-trnD,and trnS-trnG),single-copy nuclear genes(PHYP,AC5,HSP70,and AAT) from 61 individuals,as well as 11 nuclear micro satellite loci(SSR) from 102 individuals.We found relatively high genetic diversity within populations and high genetic differentiation among populations of C.panzhihuaensis,which is consistent with the patterns of other Asian inland cycads.Although no significant phylogeographical structure was detected,we found that small and unprotected populations possess higher genetic diversity and more unique haplotypes,which revises our understanding of diversity within this species and deserves due attention.Analysis of demographic dynamics suggest that human activity might be the key threat to C.panzhihuaensis.Based on the genetic characterization of C.panzhihuaensis,we propose several practical guidelines for the conservation of this species,especially for the populations with small sizes.展开更多
BACKGROUND Gastric cancer is one of the most common and deadly malignancies worldwide.Despite recent medical progress, the 5-year survival rate of gastric cancer is still unsatisfactory. 5-fluorouracil(5-Fu) is one of...BACKGROUND Gastric cancer is one of the most common and deadly malignancies worldwide.Despite recent medical progress, the 5-year survival rate of gastric cancer is still unsatisfactory. 5-fluorouracil(5-Fu) is one of the first-line antineoplastic treatments for gastric cancer, as it can effectively induce cancer cell apoptosis.However, the effect of 5-Fu is limited due to drug resistance of the malignant tumor. Previous studies have reported that Sotetsuflavone from Cycas revoluta Thunb. can markedly suppress lung cancer cell proliferation by apoptosis,though its effect on gastric cancer remains unknown.AIM To investigate the inhibitory effect of Cycas revoluta Thunb. and to determine whether it can overcome gastric cancer cell drug resistance to 5-Fu.METHODS Cell viability was examined to determine whether the natural extract of Cycas revoluta Thunb. induced gastric cancer cell death. The half-maximal effective concentration and the half-maximal lethal concentration were calculatede.Wound-healing and transwell assays were performed to examine gastric cancer cell motility. Clonogenic assays were performed to investigate the synergistic effects of Cycas revoluta Thunb. with 5-Fu, and apoptotic bodies were detected by Hoechst staining. Western blotting was performed to examine the expression of related proteins and to investigate the molecular mechanism of Cycas revoluta Thunb.-induced cancer cell apoptosis. The expressions of proteins, including mammalian target of rapamycin(mTOR) and p-AKT, were detected in different combinations of treatments for 48 h, then analyzed by ECL detection.RESULTS Gastric cancer cells were more sensitive to the natural extract of Cycas revoluta Thunb. compared to normal gastric epithelial cells, and the extract effectively inhibited gastric cancer cell migration and invasion. The extract improved the anti-cancer effect of 5-Fu by enhancing the chemosensitization of gastric cancer cells. Extract plus 5-Fu further reduced the expression of the drug-resistancerelated proteins p-AKT and mTOR after 48 h compared to 5-Fu alone. Compared to 5-Fu treatment alone, mTOR and p-AKT expression was significantly reduced by about 50% and 75%, respectively. We also found that the natural extract of Cycas revoluta Thunb. further increased 5-Fu-induced gastric cancer cell apoptosis. Expression of apoptosis-related protein X-linked inhibitor of apoptosis protein and apoptosis inducing factor were significantly reduced and increased,respectively, in the 5-Fu-resistant gastric cancer line SGC-7901/R treated with extract plus 5-Fu, while the expression of survivin did not change.CONCLUSION The natural extract of Cycas revoluta Thunb. effectively inhibited gastric cancer cell growth and enhanced the anti-cancer effect of 5-Fu through the AKT-mTOR pathway.展开更多
Geological activities and climate oscillations during the Quaternary period profoundly impacted the distribution of species in Southwest China. Some plant species may be harbored in refugia, such as the dry-hot valley...Geological activities and climate oscillations during the Quaternary period profoundly impacted the distribution of species in Southwest China. Some plant species may be harbored in refugia, such as the dry-hot valleys of Southwest China. Cycas chenii X. Gong & W. Zhou, a critically endangered cycad species, which grows under the canopy in subtropical evergreen broad-leaved forests along the upstream drainage area of the Red River, is endemic to this refugium. In this study, 60 individuals of C. chenii collected from six populations were analyzed by sequencing two chloroplast intergenic spacers(cp DNA:psb A-trn H and trn L-trn F) and two nuclear genes(PHYP and RBP-1). Results showed high genetic diversity at the species level, but low within-population genetic diversity and high interpopulation genetic differentiation. A Bayesian phylogenetic tree based on cp DNA showed that five chloroplast haplotypes were clustered into two clades, which corresponds to the division of the western and eastern bank of the Red River. These data indicate a possible role for the Red River as a geographic barrier to gene flow in C. chenii.Based on our findings, we propose appropriate in situ and ex situ conservation strategies for C. chenii.展开更多
The so-called “megasporophylls” of Ginkgoales, Coniferales, and Gnetales have been proven metamorphosed shoots, making “megasporophyll” of Cycas the last one resembling a leaf. Why and how it is so in Cycas (the m...The so-called “megasporophylls” of Ginkgoales, Coniferales, and Gnetales have been proven metamorphosed shoots, making “megasporophyll” of Cycas the last one resembling a leaf. Why and how it is so in Cycas (the most ancient seed plant dated back to the Palaeozoic) become key questions because their answers are hinged with the fates of several hypotheses in botany. Here, we performed a controlled developmental experiment on the ovulate parts (megasporophylls) in a single strobilus of Cycas sexseminifera. By removing the neighboring ones, two of the ovulate parts were left isolated spatially from others, in contrast to others left intact. A half-year-long continuous observation indicates that the isolated ovulate parts change their ovule arrangement from initial pinnate into helical pattern, while the intact ones in the same strobilus remain pinnate as usual. Since all ovulate parts are in the same strobilus and controlled by the same genome in this case and the only difference is lack of pressure from neighbors for the isolated ones, the changes in ovule orientation and ovulate part morphology can only be attributed to the lack of mechanical pressure among the ovulate parts. Therefore, we conclude that mechanical pressure, not genes, controls the morphology of ovulate parts and contributes to the leaf-like ovulate part morphology in Cycas. This conclusion cautions previous superficial interpretations of plant morphology.展开更多
A normalized full-length cDNA library was constructed from the coralloid roots of Cycas debaoensis by the DSN （duplex-specific nuclease） normalization method combined with the SMART （Switching Mechanism At 5＇ end ...A normalized full-length cDNA library was constructed from the coralloid roots of Cycas debaoensis by the DSN （duplex-specific nuclease） normalization method combined with the SMART （Switching Mechanism At 5＇ end of the RNA Transcript） technique. The titer of the original cDNA library was about 1.5 × 10^6 cfu·mL^-1 and the average insertion size was about 1 kb with a high recombination rate （97%）. The 5011 high-quality expressed sequence tags （ESTs） were obtained from 5393 randomly picked cDNA clones. Clustering and assembly of ESTs resulted in 2984 unique sequences, consisting of 618 contigs and 2366 singlets. EST sequence annotation revealed that 2333 and 1901 unigenes were functionally anno- tated in the NCBI non-redundant database and Swiss-Prot protein database, respectively. Functional analysis demonstrated that 1495 （50.1%） unigenes were associated with 4082 Gene Ontology （GO） terms. A total of 847 unigenes were grouped into 22 Cluster of Orthologous Groups （COG） functional categories. Based on the EST dataset, 22 ESTs that encoded putative receptor-like protein kinase （RLK） genes were screened. Furthermore, a total of 94 simple sequence repeats （SSRs） were discovered, of which 20 loci were successfully amplified in C debaoensis. This study is the first EST analysis for the coralloid roots of C debaoensis and provides a valuable genomic resource for novel gene discovery, gene expression and comparative genomics, conservation and management studies as well as applications in C debaoensis and related cycad species.展开更多
RNA editing is a post-transcriptional process that results in modifications of ribonucleotides at specific locations. In land plants editing can occur in both mitochondria and chloroplasts and most commonly involves C...RNA editing is a post-transcriptional process that results in modifications of ribonucleotides at specific locations. In land plants editing can occur in both mitochondria and chloroplasts and most commonly involves C-to-U changes, especially in seed plants. Using prediction and experimental determination, we investigated RNA editing in 40 protein-coding genes from the chloroplast genome of Cycas taitungensis. A total of 85 editing sites were identified in 25 transcripts. Comparison analysis of the published editotypes of these 25 transcripts in eight species showed that RNA editing events gradually disappear during plant evolution. The editing in the first and third codon position disappeared quicker than that in the second codon position, ndh genes have the highest editing frequency while serine and proline codons were more frequently edited than the codons of other amino acids. These results imply that retained RNA editing sites have imbalanced distribution in genes and most of them may function by changing protein structure or interaction. Mitochondrion protein-coding genes have three times the editing sites compared with chloroplast genes of Cycas, most likely due to slower evolution speed.展开更多
There are five wild populations of Cycas fairylakea in Guangdong Province,China,three of which are newly found.A study of the biological characteristics of C.fairylakea populations showed that this species had a narro...There are five wild populations of Cycas fairylakea in Guangdong Province,China,three of which are newly found.A study of the biological characteristics of C.fairylakea populations showed that this species had a narrow colonization area within 300 hm^(2),and an island pattern of distribution.Because of the overexploitation,urbanization,environment pollution,plant diseases,and insect pests,the wild populations and individuals of C.fairylakea decreased markedly in the past decades.All five populations have an opposite pyramid age structure,few coning plants,few seed production,and low level of seed germination rate or sterility.In conclusion,C.fairylakea in Guangdong Province was threatened seriously and an urgent need to take effective efforts to protect the plants and habitats in its location sites was required.展开更多
Chilades pandava is a dangerous insect pest of Cycas spp.,which seriously threatens the growth and development of Cycas plants.On the basis of previous studies,the paper summarized the behaviors of different insect st...Chilades pandava is a dangerous insect pest of Cycas spp.,which seriously threatens the growth and development of Cycas plants.On the basis of previous studies,the paper summarized the behaviors of different insect states of C.pandava,such as feeding,flying,resting,mating,spawning,hatching,pupation,eclosion,etc.,in order to provide a reference for effective prevention and control of C.pandava.展开更多
Living cycads show a range of archaic features which suggest that they are primitive plants. They have a long fossil record, but this unfortunately consists largely of vegetative leaves. Very few reproductive organs a...Living cycads show a range of archaic features which suggest that they are primitive plants. They have a long fossil record, but this unfortunately consists largely of vegetative leaves. Very few reproductive organs are preserved as fossils. However,展开更多
Endoreduplication is prevalent during plant growth and development,and is often correlated with large cell and organ size.Despite its prevalence,the transcriptional regulatory mechanisms underlying the transition from...Endoreduplication is prevalent during plant growth and development,and is often correlated with large cell and organ size.Despite its prevalence,the transcriptional regulatory mechanisms underlying the transition from mitotic cell division to endoreduplication remain elusive.Here,we characterize ETHYLENE-RESPONSIVEELEMENTBINDING FACTOR 4(ERF4)as a positive regulator of endoreduplication through its function as a transcriptional repressor.ERF4 was specifically expressed in mature tissues in which the cells were undergoing expansion,but was rarely expressed in young organs.Plants overexpressing ERF4 exhibited much larger cells and organs,while plants that lacked functional ERF4 displayed smaller organs than the wild-type.ERF4 was further shown to regulate cell size by controlling the endopolyploidy level in the nuclei.Moreover,ERF4 physically associates with the class I TEOSINTE BRANCHED 1/CYCLOIDEA/PCF(TCP)protein TCP15,a transcription factor that inhibits endoreduplication by activating the expression of a key cell-cycle gene,CYCLIN A2;3(CYCA2;3).A molecular and genetic analysis revealed that ERF4promotes endoreduplication by directly suppressing the expression of CYCA2;3.Together,this study demonstrates that ERF4 and TCP15 function as a module to antagonistically regulate each other?s activity in regulating downstream genes,thereby controlling the switch from the mitotic cell cycle to endoreduplication during leaf development.These findings expand our understanding of how the control of the cell cycle is fine-tuned by an ERF4–TCP15 transcriptional complex.展开更多
文摘A new C-glycosylflavone, named panzhihuacycaside (1), was isolated from the leaves of Cycas panzhihuaensis L. Zhou et S. Y. Yang (Cycadaceae) along with 2,3-dihydrohinokiflavone (2), 5,5',7,7', 4',4''-hexahydroxy-(2',8')-biflavone (3), vanillic acid (4), P-sitosterol (5) and daucosterol (6). Their structures were elucidated by spectral and chemical evidence.
基金This work was supported by the National Key R&D Program of China(2017YF0505200).The authors thank Fangming Zhang for her assistance with plant sampling,and Xiuyan Feng,Rui Yang and Yujuan Zhao for their help and discussion of data analyses.
文摘Cycas panzhihuaensis L.Zhou & S.Y.Yang(Cycadaceae) is an endangered gymnosperm species endemic to the dry-hot valley of the Jinsha River basin in southwest China.Although the wild C.panzhihuaensis population from Panzhihua Cycad Natural Reserve is well protected and its genetic diversity has been well assessed,the genetic characteristics of populations outside the nature reserve,which face larger risks of extinction,remain unknown.Furthermore,the population genetics and historical dynamics of this endemic and endangered species have not been examined across its entire range.In this study,to analyze the genetic diversity,phylogeographical structure and demographic history of C.panzhihuaensis from all its seven known locations,we sequenced and compared molecular data from chloroplastic DNA(psbA-trnH,psbM-trnD,and trnS-trnG),single-copy nuclear genes(PHYP,AC5,HSP70,and AAT) from 61 individuals,as well as 11 nuclear micro satellite loci(SSR) from 102 individuals.We found relatively high genetic diversity within populations and high genetic differentiation among populations of C.panzhihuaensis,which is consistent with the patterns of other Asian inland cycads.Although no significant phylogeographical structure was detected,we found that small and unprotected populations possess higher genetic diversity and more unique haplotypes,which revises our understanding of diversity within this species and deserves due attention.Analysis of demographic dynamics suggest that human activity might be the key threat to C.panzhihuaensis.Based on the genetic characterization of C.panzhihuaensis,we propose several practical guidelines for the conservation of this species,especially for the populations with small sizes.
文摘BACKGROUND Gastric cancer is one of the most common and deadly malignancies worldwide.Despite recent medical progress, the 5-year survival rate of gastric cancer is still unsatisfactory. 5-fluorouracil(5-Fu) is one of the first-line antineoplastic treatments for gastric cancer, as it can effectively induce cancer cell apoptosis.However, the effect of 5-Fu is limited due to drug resistance of the malignant tumor. Previous studies have reported that Sotetsuflavone from Cycas revoluta Thunb. can markedly suppress lung cancer cell proliferation by apoptosis,though its effect on gastric cancer remains unknown.AIM To investigate the inhibitory effect of Cycas revoluta Thunb. and to determine whether it can overcome gastric cancer cell drug resistance to 5-Fu.METHODS Cell viability was examined to determine whether the natural extract of Cycas revoluta Thunb. induced gastric cancer cell death. The half-maximal effective concentration and the half-maximal lethal concentration were calculatede.Wound-healing and transwell assays were performed to examine gastric cancer cell motility. Clonogenic assays were performed to investigate the synergistic effects of Cycas revoluta Thunb. with 5-Fu, and apoptotic bodies were detected by Hoechst staining. Western blotting was performed to examine the expression of related proteins and to investigate the molecular mechanism of Cycas revoluta Thunb.-induced cancer cell apoptosis. The expressions of proteins, including mammalian target of rapamycin(mTOR) and p-AKT, were detected in different combinations of treatments for 48 h, then analyzed by ECL detection.RESULTS Gastric cancer cells were more sensitive to the natural extract of Cycas revoluta Thunb. compared to normal gastric epithelial cells, and the extract effectively inhibited gastric cancer cell migration and invasion. The extract improved the anti-cancer effect of 5-Fu by enhancing the chemosensitization of gastric cancer cells. Extract plus 5-Fu further reduced the expression of the drug-resistancerelated proteins p-AKT and mTOR after 48 h compared to 5-Fu alone. Compared to 5-Fu treatment alone, mTOR and p-AKT expression was significantly reduced by about 50% and 75%, respectively. We also found that the natural extract of Cycas revoluta Thunb. further increased 5-Fu-induced gastric cancer cell apoptosis. Expression of apoptosis-related protein X-linked inhibitor of apoptosis protein and apoptosis inducing factor were significantly reduced and increased,respectively, in the 5-Fu-resistant gastric cancer line SGC-7901/R treated with extract plus 5-Fu, while the expression of survivin did not change.CONCLUSION The natural extract of Cycas revoluta Thunb. effectively inhibited gastric cancer cell growth and enhanced the anti-cancer effect of 5-Fu through the AKT-mTOR pathway.
基金supported by the United Fund of the NSFCthe Yunnan Natural Science Foundation(Grant No.U1136602 to X.G.)
文摘Geological activities and climate oscillations during the Quaternary period profoundly impacted the distribution of species in Southwest China. Some plant species may be harbored in refugia, such as the dry-hot valleys of Southwest China. Cycas chenii X. Gong & W. Zhou, a critically endangered cycad species, which grows under the canopy in subtropical evergreen broad-leaved forests along the upstream drainage area of the Red River, is endemic to this refugium. In this study, 60 individuals of C. chenii collected from six populations were analyzed by sequencing two chloroplast intergenic spacers(cp DNA:psb A-trn H and trn L-trn F) and two nuclear genes(PHYP and RBP-1). Results showed high genetic diversity at the species level, but low within-population genetic diversity and high interpopulation genetic differentiation. A Bayesian phylogenetic tree based on cp DNA showed that five chloroplast haplotypes were clustered into two clades, which corresponds to the division of the western and eastern bank of the Red River. These data indicate a possible role for the Red River as a geographic barrier to gene flow in C. chenii.Based on our findings, we propose appropriate in situ and ex situ conservation strategies for C. chenii.
文摘The so-called “megasporophylls” of Ginkgoales, Coniferales, and Gnetales have been proven metamorphosed shoots, making “megasporophyll” of Cycas the last one resembling a leaf. Why and how it is so in Cycas (the most ancient seed plant dated back to the Palaeozoic) become key questions because their answers are hinged with the fates of several hypotheses in botany. Here, we performed a controlled developmental experiment on the ovulate parts (megasporophylls) in a single strobilus of Cycas sexseminifera. By removing the neighboring ones, two of the ovulate parts were left isolated spatially from others, in contrast to others left intact. A half-year-long continuous observation indicates that the isolated ovulate parts change their ovule arrangement from initial pinnate into helical pattern, while the intact ones in the same strobilus remain pinnate as usual. Since all ovulate parts are in the same strobilus and controlled by the same genome in this case and the only difference is lack of pressure from neighbors for the isolated ones, the changes in ovule orientation and ovulate part morphology can only be attributed to the lack of mechanical pressure among the ovulate parts. Therefore, we conclude that mechanical pressure, not genes, controls the morphology of ovulate parts and contributes to the leaf-like ovulate part morphology in Cycas. This conclusion cautions previous superficial interpretations of plant morphology.
基金supported by the Grant(201522)from Shenzhen Urban Management
文摘A normalized full-length cDNA library was constructed from the coralloid roots of Cycas debaoensis by the DSN （duplex-specific nuclease） normalization method combined with the SMART （Switching Mechanism At 5＇ end of the RNA Transcript） technique. The titer of the original cDNA library was about 1.5 × 10^6 cfu·mL^-1 and the average insertion size was about 1 kb with a high recombination rate （97%）. The 5011 high-quality expressed sequence tags （ESTs） were obtained from 5393 randomly picked cDNA clones. Clustering and assembly of ESTs resulted in 2984 unique sequences, consisting of 618 contigs and 2366 singlets. EST sequence annotation revealed that 2333 and 1901 unigenes were functionally anno- tated in the NCBI non-redundant database and Swiss-Prot protein database, respectively. Functional analysis demonstrated that 1495 （50.1%） unigenes were associated with 4082 Gene Ontology （GO） terms. A total of 847 unigenes were grouped into 22 Cluster of Orthologous Groups （COG） functional categories. Based on the EST dataset, 22 ESTs that encoded putative receptor-like protein kinase （RLK） genes were screened. Furthermore, a total of 94 simple sequence repeats （SSRs） were discovered, of which 20 loci were successfully amplified in C debaoensis. This study is the first EST analysis for the coralloid roots of C debaoensis and provides a valuable genomic resource for novel gene discovery, gene expression and comparative genomics, conservation and management studies as well as applications in C debaoensis and related cycad species.
基金supported by the Fundamental Research Fund for the Central Universities (Grant No. GK200902028)
文摘RNA editing is a post-transcriptional process that results in modifications of ribonucleotides at specific locations. In land plants editing can occur in both mitochondria and chloroplasts and most commonly involves C-to-U changes, especially in seed plants. Using prediction and experimental determination, we investigated RNA editing in 40 protein-coding genes from the chloroplast genome of Cycas taitungensis. A total of 85 editing sites were identified in 25 transcripts. Comparison analysis of the published editotypes of these 25 transcripts in eight species showed that RNA editing events gradually disappear during plant evolution. The editing in the first and third codon position disappeared quicker than that in the second codon position, ndh genes have the highest editing frequency while serine and proline codons were more frequently edited than the codons of other amino acids. These results imply that retained RNA editing sites have imbalanced distribution in genes and most of them may function by changing protein structure or interaction. Mitochondrion protein-coding genes have three times the editing sites compared with chloroplast genes of Cycas, most likely due to slower evolution speed.
基金This paper was supported by the grants from the National Natural Science Foundation of China(No.30070062)the Natural Science Foundation of Guangdong Province(No.04300604 and 000975)South China Botanical Garden,the Chinese Academy of Sciences(No.2002−3293).
文摘There are five wild populations of Cycas fairylakea in Guangdong Province,China,three of which are newly found.A study of the biological characteristics of C.fairylakea populations showed that this species had a narrow colonization area within 300 hm^(2),and an island pattern of distribution.Because of the overexploitation,urbanization,environment pollution,plant diseases,and insect pests,the wild populations and individuals of C.fairylakea decreased markedly in the past decades.All five populations have an opposite pyramid age structure,few coning plants,few seed production,and low level of seed germination rate or sterility.In conclusion,C.fairylakea in Guangdong Province was threatened seriously and an urgent need to take effective efforts to protect the plants and habitats in its location sites was required.
文摘Chilades pandava is a dangerous insect pest of Cycas spp.,which seriously threatens the growth and development of Cycas plants.On the basis of previous studies,the paper summarized the behaviors of different insect states of C.pandava,such as feeding,flying,resting,mating,spawning,hatching,pupation,eclosion,etc.,in order to provide a reference for effective prevention and control of C.pandava.
文摘Living cycads show a range of archaic features which suggest that they are primitive plants. They have a long fossil record, but this unfortunately consists largely of vegetative leaves. Very few reproductive organs are preserved as fossils. However,
基金supported by the National Natural Science Foundation of China(31600237)the Agricultural Science and Technology Innovation Program(ASTIP-TRIC02)+1 种基金the Key Science and Technology Projects of Sichuan Tobacco Institute(SCYC202002)the Central Public-Interest Scientific Institution Basal Research Fund(16102320200002)。
文摘Endoreduplication is prevalent during plant growth and development,and is often correlated with large cell and organ size.Despite its prevalence,the transcriptional regulatory mechanisms underlying the transition from mitotic cell division to endoreduplication remain elusive.Here,we characterize ETHYLENE-RESPONSIVEELEMENTBINDING FACTOR 4(ERF4)as a positive regulator of endoreduplication through its function as a transcriptional repressor.ERF4 was specifically expressed in mature tissues in which the cells were undergoing expansion,but was rarely expressed in young organs.Plants overexpressing ERF4 exhibited much larger cells and organs,while plants that lacked functional ERF4 displayed smaller organs than the wild-type.ERF4 was further shown to regulate cell size by controlling the endopolyploidy level in the nuclei.Moreover,ERF4 physically associates with the class I TEOSINTE BRANCHED 1/CYCLOIDEA/PCF(TCP)protein TCP15,a transcription factor that inhibits endoreduplication by activating the expression of a key cell-cycle gene,CYCLIN A2;3(CYCA2;3).A molecular and genetic analysis revealed that ERF4promotes endoreduplication by directly suppressing the expression of CYCA2;3.Together,this study demonstrates that ERF4 and TCP15 function as a module to antagonistically regulate each other?s activity in regulating downstream genes,thereby controlling the switch from the mitotic cell cycle to endoreduplication during leaf development.These findings expand our understanding of how the control of the cell cycle is fine-tuned by an ERF4–TCP15 transcriptional complex.
