Heat stress can restrict plant growth,development,and crop yield.As essential plant antioxidants,carotenoids play significant roles in plant stress resistance.b-carotene hydroxylase(BHY)and b-carotene ketolase(BKT),wh...Heat stress can restrict plant growth,development,and crop yield.As essential plant antioxidants,carotenoids play significant roles in plant stress resistance.b-carotene hydroxylase(BHY)and b-carotene ketolase(BKT),which catalyze the conversions of b-carotene to zeaxanthin and b-carotene to canthaxanthin,respectively,are key enzymes in the carotenoid biosynthetic pathway,but little is known about their potential functions in stress resistance.Here,we investigated the roles of b-carotene hydroxylase and b-carotene ketolase during heat stress in Physcomitrella patens through expressing a b-carotene ketolase gene from Chlamydomonas reinhardtii(Cr BKT)and a b-carotene hydroxylase gene from Haematococcus pluvialis(Hp BHY)in the moss P.patens.In transgenic moss expressing these genes,carotenoids content increased(especially lutein content),and heat stress tolerance increased,with reduced leafy tissue necrosis.To investigate the mechanism of this heat stress resistance,we measured various physiological indicators and found a lower malondialdehyde level,higher peroxidase and superoxide dismutase activities,and higher endogenous abscisic acid and salicylate content in the transgenic plants in response to high-temperature stress.These results demonstrate that Cr BKT and Hp BHY increase plant heat stress resistance through the antioxidant and damage repair metabolism,which is related to abscisic acid and salicylate signaling.展开更多
Establishing a transgenic plant largely relies on a selectable marker gene that can confer antibiotic or herbicide resistance to plant cells.The existence of such selectable marker genes in genetically modified foods ...Establishing a transgenic plant largely relies on a selectable marker gene that can confer antibiotic or herbicide resistance to plant cells.The existence of such selectable marker genes in genetically modified foods has long been criticized.Plant cells generally exhibit too low an activity of phosphomannose isomerase(PMI)to grow with mannose as a sole carbon source.In this study,we characterized PMI from the green microalga Chlorococcum sp.and assessed its feasibility as a selectable marker for plant biotechnology.Chlorococcum sp.PMI(ChlPMI)was shown to be closely related to higher plants but more distant to bacterial counterparts.Overexpression of ChlPMI in tomato induced callus and shoot formation in media containing mannose(6 g/L)and had an average transformation rate of 3.9%.Based on this transformation system,a polycistronic gene cluster containing crtB,HpBHY,CrBKT and SlLCYB(BBBB)was co-expressed in a different tomato cultivar.Six putative transformants were achieved with a transformation rate of 1.4%,which produced significant amounts of astaxanthin due to the expression of the BBBB genes.Taken together,these findings indicate that we have established an additional tool for plant biotechnology that may be suitable for genetically modifying foods safely.展开更多
With the diversified development of the battery industry,potassium-ion batteries(PIBs)have aroused widespread interest due to their safety and high potassium reserves on earth.However,the lack of suitable anode materi...With the diversified development of the battery industry,potassium-ion batteries(PIBs)have aroused widespread interest due to their safety and high potassium reserves on earth.However,the lack of suitable anode materials limits their development and application to a certain extent.Based on first-principles calculations,we investigate the possibility of using PC_(3) monolayer as the anode material for PIBs.PC_(3)sheet has excellent electrical properties and meets the prerequisite of anode materials.The storage capacity of potassium is as high as 1200 mAh·g^(-1),which is better than many other reported potassium-ion anode materials.In addition,the outstanding advantages of PC_(3)sheet,such as low diffusion barrier and moderate open-circuit voltage,make it a potential anode candidate for PIBs.展开更多
We report on the observation of the highly forbidden ^1S0–^3P0 optical clock transition in laser-cooled ^199Hg atoms.More than 95% depletion of cold ^199Hg atoms is detected in the magneto-optical trap. Using the fre...We report on the observation of the highly forbidden ^1S0–^3P0 optical clock transition in laser-cooled ^199Hg atoms.More than 95% depletion of cold ^199Hg atoms is detected in the magneto-optical trap. Using the free-of-field detection method, the AC Stark shift from the cooling laser is removed from the in-field spectroscopy. At low-power clock laser pumping, the linewidth of the clock spectroscopy is approximately 450 k Hz（full width at half-maximum）, which corresponds to a Doppler broadening at the atom temperature of 60 μK. We determine the -1S0–^13P0transition frequency to be 1,128,575,290.819（14） MHz by referencing with a hydrogen maser and measuring with a fiber optical frequency comb. Moreover, a weak Doppler-free signal is observed.展开更多
We demonstrate the frequency stabilization of a 1.55 μm erbium-doped fiber laser by locking it to a 5-km-long optical fiber delay line(FDL).The stabilized laser is characterized via comparison with a second identical...We demonstrate the frequency stabilization of a 1.55 μm erbium-doped fiber laser by locking it to a 5-km-long optical fiber delay line(FDL).The stabilized laser is characterized via comparison with a second identical laser system.We obtain a fractional frequency stability of better than 3 × 10^-15 over time scales of 1–10 s and a laser linewidth of 0.2 Hz, which is the narrowest linewidth of an FDL-stabilized laser observed to date.展开更多
Excess frequency noise induced by mechanical vibration is the dominant noise source at low Fourier frequencies in fiber-delay-line stabilized lasers. To resolve this problem, a double-winding fiber spool is designed a...Excess frequency noise induced by mechanical vibration is the dominant noise source at low Fourier frequencies in fiber-delay-line stabilized lasers. To resolve this problem, a double-winding fiber spool is designed and implemented that has ultralow acceleration sensitivity in all spatial directions. By carefully choosing the optimal geometry parameters of the fiber spool, we achieve acceleration sensitivity of 8 × 10^-11/g and 3 × 10^-11/g(g denotes the gravitational acceleration) in axial and radial directions, respectively.展开更多
基金supported by the CAS Pioneer Hundred Talents Programthe National Natural Science Foundation of China (31571262)Yunnan Natural Science Foundation (2017FB031)
文摘Heat stress can restrict plant growth,development,and crop yield.As essential plant antioxidants,carotenoids play significant roles in plant stress resistance.b-carotene hydroxylase(BHY)and b-carotene ketolase(BKT),which catalyze the conversions of b-carotene to zeaxanthin and b-carotene to canthaxanthin,respectively,are key enzymes in the carotenoid biosynthetic pathway,but little is known about their potential functions in stress resistance.Here,we investigated the roles of b-carotene hydroxylase and b-carotene ketolase during heat stress in Physcomitrella patens through expressing a b-carotene ketolase gene from Chlamydomonas reinhardtii(Cr BKT)and a b-carotene hydroxylase gene from Haematococcus pluvialis(Hp BHY)in the moss P.patens.In transgenic moss expressing these genes,carotenoids content increased(especially lutein content),and heat stress tolerance increased,with reduced leafy tissue necrosis.To investigate the mechanism of this heat stress resistance,we measured various physiological indicators and found a lower malondialdehyde level,higher peroxidase and superoxide dismutase activities,and higher endogenous abscisic acid and salicylate content in the transgenic plants in response to high-temperature stress.These results demonstrate that Cr BKT and Hp BHY increase plant heat stress resistance through the antioxidant and damage repair metabolism,which is related to abscisic acid and salicylate signaling.
基金supported by a grant from Yunnan high talents program(Y33D331),Yunnan Province,China.
文摘Establishing a transgenic plant largely relies on a selectable marker gene that can confer antibiotic or herbicide resistance to plant cells.The existence of such selectable marker genes in genetically modified foods has long been criticized.Plant cells generally exhibit too low an activity of phosphomannose isomerase(PMI)to grow with mannose as a sole carbon source.In this study,we characterized PMI from the green microalga Chlorococcum sp.and assessed its feasibility as a selectable marker for plant biotechnology.Chlorococcum sp.PMI(ChlPMI)was shown to be closely related to higher plants but more distant to bacterial counterparts.Overexpression of ChlPMI in tomato induced callus and shoot formation in media containing mannose(6 g/L)and had an average transformation rate of 3.9%.Based on this transformation system,a polycistronic gene cluster containing crtB,HpBHY,CrBKT and SlLCYB(BBBB)was co-expressed in a different tomato cultivar.Six putative transformants were achieved with a transformation rate of 1.4%,which produced significant amounts of astaxanthin due to the expression of the BBBB genes.Taken together,these findings indicate that we have established an additional tool for plant biotechnology that may be suitable for genetically modifying foods safely.
基金the National Natural Science Foundation of China(Grant Nos.11574167 and 11874033)the KC Wong Magna Foundation in Ningbo University.
文摘With the diversified development of the battery industry,potassium-ion batteries(PIBs)have aroused widespread interest due to their safety and high potassium reserves on earth.However,the lack of suitable anode materials limits their development and application to a certain extent.Based on first-principles calculations,we investigate the possibility of using PC_(3) monolayer as the anode material for PIBs.PC_(3)sheet has excellent electrical properties and meets the prerequisite of anode materials.The storage capacity of potassium is as high as 1200 mAh·g^(-1),which is better than many other reported potassium-ion anode materials.In addition,the outstanding advantages of PC_(3)sheet,such as low diffusion barrier and moderate open-circuit voltage,make it a potential anode candidate for PIBs.
基金supported by the National Natural Science Foundation of China(NSFC)(No.91436105)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB21030200)
文摘We report on the observation of the highly forbidden ^1S0–^3P0 optical clock transition in laser-cooled ^199Hg atoms.More than 95% depletion of cold ^199Hg atoms is detected in the magneto-optical trap. Using the free-of-field detection method, the AC Stark shift from the cooling laser is removed from the in-field spectroscopy. At low-power clock laser pumping, the linewidth of the clock spectroscopy is approximately 450 k Hz（full width at half-maximum）, which corresponds to a Doppler broadening at the atom temperature of 60 μK. We determine the -1S0–^13P0transition frequency to be 1,128,575,290.819（14） MHz by referencing with a hydrogen maser and measuring with a fiber optical frequency comb. Moreover, a weak Doppler-free signal is observed.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.11604353,11274324,and 11704391)the Key Research Program of the Chinese Academy of Sciences(No.KJZD-EWW02)
文摘We demonstrate the frequency stabilization of a 1.55 μm erbium-doped fiber laser by locking it to a 5-km-long optical fiber delay line(FDL).The stabilized laser is characterized via comparison with a second identical laser system.We obtain a fractional frequency stability of better than 3 × 10^-15 over time scales of 1–10 s and a laser linewidth of 0.2 Hz, which is the narrowest linewidth of an FDL-stabilized laser observed to date.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.11034008,11274324,and 11604353)the Key Research Program of the Chinese Academy of Sciences(No.KJZD-EW-W02)
文摘Excess frequency noise induced by mechanical vibration is the dominant noise source at low Fourier frequencies in fiber-delay-line stabilized lasers. To resolve this problem, a double-winding fiber spool is designed and implemented that has ultralow acceleration sensitivity in all spatial directions. By carefully choosing the optimal geometry parameters of the fiber spool, we achieve acceleration sensitivity of 8 × 10^-11/g and 3 × 10^-11/g(g denotes the gravitational acceleration) in axial and radial directions, respectively.
