Enhancing photosynthetic efficiency is a major goal for improving crop yields under agricultural field conditions and is associated with chloroplast biosynthesis and development.In this study,we demonstrate that Golde...Enhancing photosynthetic efficiency is a major goal for improving crop yields under agricultural field conditions and is associated with chloroplast biosynthesis and development.In this study,we demonstrate that Golden2-like 1a(BnGLK1a)plays an important role in regulating chloroplast development and photosynthetic efficiency.Overexpressing BnGLK1a resulted in significant increases in chlorophyll content,the number of thylakoid membrane layers and photosynthetic efficiency in Brassica napus,while knocking down BnGLK1a transcript levels through RNA interference(RNAi)had the opposite effects.A yeast two-hybrid screen revealed that BnGLK1a interacts with the abscisic acid receptor PYRABACTIN RESISTANCE 1-LIKE 1-2(BnPYL1-2)and CONSTITUTIVE PHOTOMORPHOGENIC 9 SIGNALOSOME 5A subunit(BnCSN5A),which play essential roles in regulating chloroplast development and photosynthesis.Consistent with this,BnGLK1a-RNAi lines of B.napus display hypersensitivity to the abscisic acid(ABA)response.Importantly,overexpression of BnGLK1a resulted in a 10%increase in thousand-seed weight,whereas seeds from BnGLK1a-RNAi lines were 16%lighter than wild type.We propose that BnGLK1a could be a potential target in breeding for improving rapeseed productivity.Our results not only provide insights into the mechanisms of BnGLK1a function,but also offer a potential approach for improving the productivity of Brassica species.展开更多
Plant chlorophyll biosynthesis and chloroplast development are two complex processes that are regulated by exogenous and endogenous factors. In this study, we identified OsDXR, a gene encoding a reductoisomerase that ...Plant chlorophyll biosynthesis and chloroplast development are two complex processes that are regulated by exogenous and endogenous factors. In this study, we identified OsDXR, a gene encoding a reductoisomerase that positively regulates chlorophyll biosynthesis and chloroplast development in rice. OsDXR knock-out lines displayed the albino phenotype and could not complete the whole life cycle process. OsDXR was highly expressed in rice leaves, and subcellular localization indicated that OsDXR is a chloroplast protein. Many genes involved in chlorophyll biosynthesis and chloroplast development were differentially expressed in the OsDXR knock-out lines compared to the wild type.Moreover, we found that the RNA editing efficiencies of ndhA-1019 and rpl2-1 were significantly reduced in the OsDXR knock-out lines. Furthermore, OsDXR interacted with the RNA editing factor OsMORF1 in a yeast two-hybrid screen and bimolecular fluorescence complementation assay. Finally, disruption of the plastidial 2-C-methyl-derythritol-4-phosphate pathway resulted in defects in chloroplast development and the RNA editing of chloroplast genes.展开更多
The nuclear-encoded factors and the photosynthetic apparatus have been studied extensively during chloroplast biogenesis.However,many questions regarding these processes remain unanswered,particularly in perennial woo...The nuclear-encoded factors and the photosynthetic apparatus have been studied extensively during chloroplast biogenesis.However,many questions regarding these processes remain unanswered,particularly in perennial woody plants.As a model material of woody plants,poplar not only has very significant value of research,but also possesses economic and ecological properties.This study reports the Populus trichocarpa DJ-1C(PtrDJ1C)factor,encoded by a nuclear gene,and a member of the DJ-1 superfamily.PtrDJ1C knock-out with the CRISPR/Cas9 system resulted in different albino phenotypes.Chlorophyll fluorescence and immunoblot analyses showed that the levels of photosynthetic complex proteins decreased significantly.Moreover,the transcript level of plastid-encoded RNA polymerase-dependent genes and the splicing efficiency of several introns were affected in the mutant line.Furthermore,rRNA accumulation was abnormal,leading to developmental defects in chloroplasts and affecting lignin accumulation.We concluded that the PtrDJ1C protein is essential for early chloroplast development and lignin deposition in poplar.展开更多
Photosynthesis occurs mainly in chloroplasts,whose development is regulated by proteins encoded by nuclear genes.Among them,pentapeptide repeat(PPR)proteins participate in organelle RNA editing.Although there are more...Photosynthesis occurs mainly in chloroplasts,whose development is regulated by proteins encoded by nuclear genes.Among them,pentapeptide repeat(PPR)proteins participate in organelle RNA editing.Although there are more than 450 members of the PPR protein family in rice,only a few affect RNA editing in rice chloroplasts.Gene editing technology has created new rice germplasm and mutants,which could be used for rice breeding and gene function study.This study evaluated the functions of OsPPR9 in chloroplast RNA editing in rice.The osppr9 mutants were obtained by CRISPR/Cas9,which showed yellowing leaves and a lethal phenotype,with suppressed expression of genes associated with chloroplast development and accumulation of photosynthetic-related proteins.In addition,loss of OsPPR9 protein function reduces the editing efficiency of rps8-C182,rpoC2-C4106,rps14-C80,and ndhB-C611 RNA editing sites,which affects chloroplast growth and development in rice.Our data showed that OsPPR9 is highly expressed in rice leaves and encodes a DYW-PPR protein localized in chloroplasts.Besides,the OsPPR9 protein was shown to interact with OsMORF2 and OsMORF9.Together,our findings provide insights into the role of the PPR protein in regulating chloroplast development in rice.展开更多
Pentatricopeptide repeat(PPR) proteins function in post-transcriptional regulation of organellar gene expression. Although several PPR proteins are known to function in chloroplast development in rice(Oryza sativa), t...Pentatricopeptide repeat(PPR) proteins function in post-transcriptional regulation of organellar gene expression. Although several PPR proteins are known to function in chloroplast development in rice(Oryza sativa), the detailed molecular functions of many PPR proteins remain unclear.Here, we characterized a rice young leaf white stripe(ylws) mutant, which has defective chloroplast development during early seedling growth.Map-based cloning revealed that YLWS encodes a novel P-type chloroplast-targeted PPR protein with 11 PPR motifs. Further expression analyses showed that many nuclear-and plastid-encoded genes in the ylws mutant were significantly changed at the RNA and protein levels. The ylws mutant was impaired in chloroplast ribosome biogenesis and chloroplast development under low-temperature conditions. The ylws mutation causes defects in the splicing of atpF, ndhA, rpl2,and rps12, and editing of ndhA, ndhB, and rps14transcripts. YLWS directly binds to specific sites in the atpF, ndhA, and rpl2 pre-mRNAs. Our results suggest that YLWS participates in chloroplast RNA group II intron splicing and plays an important role in chloroplast development during early leaf development.展开更多
The cytochrome b_(6f)(Cyt b_(6f))complex is a multisubunit protein complex in chloroplast thylakoid membranes required for photosynthetic electron transport.Here we report the isolation and characterization of the new...The cytochrome b_(6f)(Cyt b_(6f))complex is a multisubunit protein complex in chloroplast thylakoid membranes required for photosynthetic electron transport.Here we report the isolation and characterization of the new tiny albino 1(nta1)mutant in Arabidopsis,which has severe defects in Cyt b_(6f) accumulation and chloroplast development.Gene cloning revealed that the nta1 phenotype was caused by disruption of a single nuclear gene,NTA1,which encodes an integral thylakoid membrane protein conserved across green algae and plants.Overexpression of NTA1 completely rescued the nta1 phenotype,and knockout of NTA1 in wild-type plants recapitulated the mutant phenotype.Loss of NTA1 function severely impaired the accumulation of multiprotein complexes related to photosynthesis in thylakoid membranes,particularly the components of Cyt b_(6f).NTA1 was shown to directly interact with four subunits(Cyt b6/PetB,PetD,PetG,and PetN)of Cyt b_(6f) through the DUF1279 domain and C-terminal sequence to mediate their assembly.Taken together,our results identify NTA1 as a new and key regulator of chloroplast development that plays essential roles in assembly of the Cyt b_(6f) complex by interacting with multiple Cyt b_(6f) subunits.展开更多
Pentatricopeptide repeat (PPR) proteins, charac- terized by tandem arrays of a 35 amino acid motif, have been suggested to play central and broad roles in modulating the expression of organelle genes in plants. Howe...Pentatricopeptide repeat (PPR) proteins, charac- terized by tandem arrays of a 35 amino acid motif, have been suggested to play central and broad roles in modulating the expression of organelle genes in plants. However, the molecular mechanisms of most rice PPR genes remains unclear. In this paper, we isolated and characterized a temperature-conditional virescent mutant, OsV4, in rice (Oryza sativa cultivar Jiahual (WT, japonica rice variety)). The mutant displays albino phenotype and abnormal chloroplasts at the three leaf stage, which gradually turns green after the four leaf stage at a low temperature (20℃). But the mutant always develops green leaves and well-developed chloroplasts at a high temperature (32℃). Genetic and molecular analyses uncovered that OsV4 encodes a novel chloroplast-targeted PPR protein including four PPR motifs. Further investigations show that the mutant phenotype is associated with changes in chlorophyll content and chloroplast development. The OsV4 transcripts only accumulate to high levels in young leaves, indicating that its expression is tissue-specific. In addition, transcript levels of some ribosomal components and plastid- encoded polymerase-dependent genes are dramatically re- duced in the albino mutants grown at 20℃. These findings suggest that OsV4 plays an important role during early chloroplast development under cold stress in rice.展开更多
Although the multiple organellar RNA editing factors (MORFs) in the plastids of Arabidopsis thaliana have been extensively studied, molecular details underlying how MORFs affect plant development in other species, p...Although the multiple organellar RNA editing factors (MORFs) in the plastids of Arabidopsis thaliana have been extensively studied, molecular details underlying how MORFs affect plant development in other species, particularly in rice, remain largely unknown. Here we describe the characterization of wspl, a rice mutant with white-stripe leaves and panicles. Notably, wspl exhibited nearly white immature panicles at the heading stage. Transmission electron microscopy analysis and chlorophyll content measurement re- veale i a chloroplast developmental defect and reduced chlorophyll accumulation in wspl. Positional cloning of WSP1 found a point mutation in OsO4g51280, whose putative product shares high sequence similarity with MORF proteins. Complementation experiments demonstrated that WSP1 was responsible for the variegated phenotypes of wspl. WSP1 is localized to chloroplasts and the point mutation in wspl affected the editing of multiple organellar RNA sites. Owing to the defect in plastid RNA editing, chloroplast ribosome biogenesis and ndhA splicing were also impaired in wspl, which may affect normal chloroplast development in the leaves and panicles at the heading stage. Together, our results demonstrate the importance of rice WSP1 protein in chloroplast development and broaden our knowledge about MORF family members in rice.展开更多
Functional chloroplast generation depends on the precise coordination of gene expression between the plastid and the nucleus and is essential for plant growth and development. In this study, a rice(Oryza sativa) mut...Functional chloroplast generation depends on the precise coordination of gene expression between the plastid and the nucleus and is essential for plant growth and development. In this study, a rice(Oryza sativa) mutant that exhibited albino and seedling-lethal phenotypes was isolated from a60Co-irradiated rice population. The mutant gene was identified as an ortholog of the Arabidopsis plastid transcriptionally active chromosome protein 2(p TAC2) gene, and the mutant strain was designated osptac2. Sequence and transcription analyses showed that Osp TAC2 encodes a putative chloroplast protein consisting of 10 pentratricopeptide repeat(PPR) domains and a C-terminal small Mut S-related(SMR) domain. Cytological observations via microscopy showed that the Osp TAC2-green fluorescent fusion protein is localized in the chloroplasts. Transmission electron microscopy revealed that the chloroplast of the osptac2 mutant lacks an organized thylakoid membrane. The transcript levels of all investigated PEP(plastid-encoded RNA polymerase)-dependent genes were dramatically reduced in the osptac2 mutant, whereas the transcript levels of NEP(nuclear-encoded polymerase)-dependent genes were increased. These results suggest that Osp TAC2 plays a critical role in chloroplast development and indicate that the molecular function of the Osp TAC2 gene is conserved in rice and Arabidopsis.展开更多
Plants contain various factors that transiently interact with subunits or intermediates of the thylakoid multiprotein complexes, promoting their stable association and integration. Hence, assembly factors are essentia...Plants contain various factors that transiently interact with subunits or intermediates of the thylakoid multiprotein complexes, promoting their stable association and integration. Hence, assembly factors are essential for chloroplast development and the transition from heterotrophic to phototrophic growth. Snowy cotyledon 2 (SCO2) is a DNAJ-like protein involved in thylakoid membrane biogenesis and interacts with the light-harvesting chlorophyll-binding protein LHCBI. In Arabidopsis thaliana, SCO2 function was previ- ously reported to be restricted to cotyledons. Here we show that disruption of SC02 in Lotus japonicus results not only in paler cotyledons but also in variegated true leaves. Furthermore, smaller and pale- green true leaves can also be observed in A. thaliana sco2 (atsco2) mutants under short-day conditions. In both species, SCO2 is required for proper accumulation of PSlI-LHCll complexes. In contrast to other variegated mutants, inhibition of chloroplastic translation strongly affects L. japonicus sco2 mutant devel- opment and fails to suppress their variegated phenotype. Moreover, inactivation of the suppressor of variegation AtClpR1 in the atsco2 background results in an additive double-mutant phenotype with variegated true leaves. Taken together, our results indicate that SCO2 plays a distinct role in PSll assembly or repair and constitutes a novel factor involved in leaf variegation.展开更多
Mutants with abnormal leaf coloration are good genetic materials for understanding the mechanism of chloroplast development and chlorophyll biosynthesis. In this study, a rice mutant st2 (stripe2) with stripe leaves...Mutants with abnormal leaf coloration are good genetic materials for understanding the mechanism of chloroplast development and chlorophyll biosynthesis. In this study, a rice mutant st2 (stripe2) with stripe leaves was identified from the "y-ray irradiated mutant pool. The st2 mutant exhibited decreased accumulation of chlorophyll and aberrant chloroplasts. Genetic analysis indicated that the st2 mutant was controlled by a single recessive locus. The ST2 gene was finely confined to a 27-kb region on chromosome 1 by the map-based cloning strategy and a 5-bp deletion in Os01g0765000 was identified by sequence analysis. The deletion happened in the joint of exon 3 and intron 3 and led to new spliced products of mRNA. Genetic comptementation confirmed that Os01g0765000 is the ST2 gene. We found that the ST2 gene was expressed ubiquitously. Subcellular localization assay showed that the ST2 protein was located in mitochondria. ST2 belongs to the cytidine deaminase-like family and possibly functions as the dCMP deaminase, which catalyzes the formation of dUMP from dCMP by deamination. Additionally, exogenous application of dUMP could partially rescue the st2 phenotype. Therefore, our study identified a putative dCMP deaminase as a novel regulator in chloroplast development for the first time.展开更多
Pentatricopeptide repeat(PPR)proteins play important roles in the post-transcriptional modification of organellar RNAs in plants.However,the function of most PPR proteins remains unknown.Here,we characterized the rice...Pentatricopeptide repeat(PPR)proteins play important roles in the post-transcriptional modification of organellar RNAs in plants.However,the function of most PPR proteins remains unknown.Here,we characterized the rice(Oryza sativa L.)chlorophyll deficient 4(cde4)mutant which exhibits an albino phenotype during early leaf development,with decreased chlorophyll contents and abnormal chloroplasts at low-temperature(20℃).Positional cloning revealed that CDE4 encodes a P-type PPR protein localized in chloroplasts.In the cde4 mutant,plastid-encoded polymerase(PEP)-dependent transcript levels were significantly reduced,but transcript levels of nuclear-encoded genes were increased compared to wild-type plants at 20℃.CDE4 directly binds to the transcripts of the chloroplast genes rpl2,ndhA,and ndhB.Intron splicing of these transcripts was defective in the cde4 mutant at 20℃,but was normal at 32℃.Moreover,CDE4 interacts with the guanylate kinase VIRESCENT 2(V2);overexpression of V2 enhanced CDE4 protein stability,thereby rescuing the cde4 phenotype at 20℃.Our results suggest that CDE4 participates in plastid RNA splicing and plays an important role in rice chloroplast development under lowtemperature conditions.展开更多
Chloroplast genes are transcribed by the plastidencoded RNA polymerase(PEP) or nucleus-encoded RNA polymerase. FRUCTOKINASE-LIKE PROTEINS(FLNs) are phosphofructokinase-B(Pfk B)-type carbohydrate kinases that act...Chloroplast genes are transcribed by the plastidencoded RNA polymerase(PEP) or nucleus-encoded RNA polymerase. FRUCTOKINASE-LIKE PROTEINS(FLNs) are phosphofructokinase-B(Pfk B)-type carbohydrate kinases that act as part of the PEP complex; however, the molecular mechanisms underlying FLN activity in rice remain elusive.Previously, we identified and characterized a heat-stress sensitive albino(hsa_1) mutant in rice. Map-based cloning revealed that HSA_1 encodes a putative OsFLN_2. Here, we further demonstrated that knockdown or knockout of the OsFLN_1, a close homolog of HSA_1/OsFLN_2, considerably inhibits chloroplast biogenesis and the fln_1 knockout mutants, created by clustered regularly interspaced short palindromic repeats(CRISPR) and CRISPR-associate protein_9, exhibit severe albino phenotype and seedling lethality. Moreover, OsFLN_1 localizes to the chloroplast.Yeast two-hybrid, pull-down and bimolecular fluorescencecomplementation experiments revealed that OsFLN_1 and HSA_1/OsFLN_2 interact with THIOREDOXINZ(OsTRXz) to regulate chloroplast development. In agreement with this,knockout of OsTRXz resulted in a similar albino and seedling lethality phenotype to that of the fln_1 mutants. Quantitative reverse transcription polymerase chain reaction and immunoblot analysis revealed that the transcription and translation of PEP-dependent genes were strongly inhibited in fln_1 and trxz mutants, indicating that loss of OsFLN_1, HSA_1/OsFLN_2, or OsTRXz function perturbs the stability of the transcriptionally active chromosome complex and PEP activity. These results show that OsFLN_1 and HSA_1/OsFLN_2 contribute to chloroplast biogenesis and plant growth.展开更多
Leaf color mutants in higher plants are considered to be ideal materials for studying the chlorophyll biosynthesis,photosynthesis mechanism and chloroplast development.Herein,we identified a spontaneous mutant,yc412,i...Leaf color mutants in higher plants are considered to be ideal materials for studying the chlorophyll biosynthesis,photosynthesis mechanism and chloroplast development.Herein,we identified a spontaneous mutant,yc412,in cultivated cucumber that exhibited yellow cotyledons.The yellow-lethal mutant was diagnosed with an abnormal chloroplast ultrastructure,and reduced photosynthetic capacity and pigment content.Through bulked segregant analysis-based whole-genome sequencing and fine genetic mapping,we narrowed the yellow cotyledons (yc) locus to a 96.8 kb interval on chromosome 3.By resequencing and molecular cloning,we showed that Csyc is a potential candidate gene,which encodes a yellow stripe-like (YSL) transporter.The T to C mutation in the promoter region of Csyc caused the yellow cotyledon phenotype in yc412.Compared to YZU027A (WT),the expression of Csyc was significantly downregulated in the cotyledons of yc412.Silencing of Csyc in cucumber via virus-induced gene silencing resulted in chlorotic leaves,mainly by suppressing the chlorophyll content.Furthermore,a comparative transcriptome analysis revealed that chloroplast-related genes and chlorophyll biosynthesis genes were significantly downregulated in yc412 cotyledons.Our results provide new insights into the molecular function of the YSL transporter in plant chloroplast development and chlorophyll synthesis.展开更多
Plant architecture strongly influences rice grain yield.We report the cloning and characterization of the LTA1 gene,which simultaneously controls tiller angle and yield of rice.LTA1 encodes a chloroplastlocalized prot...Plant architecture strongly influences rice grain yield.We report the cloning and characterization of the LTA1 gene,which simultaneously controls tiller angle and yield of rice.LTA1 encodes a chloroplastlocalized protein with a conserved YbaB DNA-binding domain,and is highly expressed in photosynthetic tissues including leaves and leaf sheaths.Disrupting the function of LTA1 leads to large tiller angle and yield reduction of rice.LTA1 affects the gravity response by mediating the distribution of endogenous auxin,thereby regulating the tiller angle.An lta1 mutant showed abnormal chloroplast development and decreased chlorophyll content and photosynthetic rate,in turn leading to reduction of rice yield.Our findings shed light on the genetic basis of tiller angle and provide a potential gene resource for the improvement of plant architecture and rice yield.展开更多
A nuclear-encoded sigma(σ) factor is essential for the transcriptional regulation of plant chloroplastencoded genes. Five putative maize r factors have been identified by database searches, but their functions are un...A nuclear-encoded sigma(σ) factor is essential for the transcriptional regulation of plant chloroplastencoded genes. Five putative maize r factors have been identified by database searches, but their functions are unknown. We report a maize leaf color mutant etiolated/albino leaf 1(eal1) that was derived from space mutation breeding. The eal1 mutant displays etiolated or albino leaves that then gradually turn to normal green at the seedling stage. The changes in eal1 leaf color are associated with changes in photosynthetic pigment content and chloroplast development. Map-based cloning revealed that a single amino-acid deletion changing Val_(480)-Val_(481)-Val_(482) to Val_(480)-Val_(481), in the C-terminal domain σ_(4) of the putative σ factor ZmSig2A, is responsible for the eal1 mutation. In comparison with the expression level of the wild-type(WT) allele ZmSig2A^(+) in WT plants, much higher expression of the mutant allele ZmSig2A^(⊿V) in eal1 plants was detected before the eal1 plants turned to normal green. ZmSig2A shows the highest similarity to rice OsSig2A and Arabidopsis SIG2. Ectopic expression of ZmSig2A^(+) or ZmSig2A^(⊿V) driven by the cauliflower mosaic virus 35 S promoter rescued the pale green leaf of the sig2 mutant, but ectopic expression of ZmSig2A^(⊿V) driven by the SIG2 promoter did not. We propose that the Val deletion generated a new weak allele of ZmSig2A that cannot completely abolish the ZmSig2A function. Some genes involved in chloroplast development and photosynthesis-associated nuclear genes showed significant expression differences between eal1 and WT plants. We conclude that ZmSig2A encoding a r factor is essential for maize chloroplast development. The eal1 mutant with a weak allele of ZmSig2A represents a valuable genetic resource for investigating the regulation of ZmSig2A-mediated chloroplast development in maize.The eal1 mutation may be useful as a marker for early identification and elimination of false hybrids or transgene transmission in the application of genetic male sterility to commercial hybrid seed production.展开更多
Chloroplasts are important for plant growth and development.RNA editing in chloroplast converts cytidines(Cs)to uridine s(Us)at specific transcript positions and provides a correction mechanism to restore conserved co...Chloroplasts are important for plant growth and development.RNA editing in chloroplast converts cytidines(Cs)to uridine s(Us)at specific transcript positions and provides a correction mechanism to restore conserved codons or creates start or stop codons.However,the underlined molecular mechanism is not yet fully unders tood.In the present study,we identi fied a thermo-sensi tive mutantin leaf color 1(tst1)and found that TSL1 is allelic to DELAYED GREENING 1(DG1).The mis sense mutation of DG1 in tsl1 mutant confers a high temperature sensitivity and impaired chloroplast development at an elevated ambient temperature in Arabidopsis.Subsequent analysis showed that chloroplast RNA editing at seve ral sites including accD-2568,ndhD-2,and petL-5 is impaired in tsl1 mutant plants grown at an elevated temperature.DG1 interacts with MORF2 and other proteins such as DYW1 and DYW2 involved in chloroplast RNA editing.In vitro RNA electrophoretic mobility shift assay demonstrated that DG1 binds to RNA targets such as accD,ndhD,and petL.Thus,our results revealed that DG1 is important for maintaining chloroplast mRNA editing in Arabidopsis.展开更多
Albino mutants are useful genetic resource for studying chlorophyll biosynthesis and chloroplast development and cloning genes involved in these processes in plants. Here we report a novel rice mutant low temperature ...Albino mutants are useful genetic resource for studying chlorophyll biosynthesis and chloroplast development and cloning genes involved in these processes in plants. Here we report a novel rice mutant low temperature albino I (ltal) that showed albino leaves before 4-leaf stage when grown under temperature lower than 20℃, but developed normal green leaves under temperature higher than 24℃ or similar morphological phenotypes in dark as did the wild-type (WT). Our analysis showed that the contents of chlorophylls and chlo- rophyll precursors were remarkably decreased in the Ital mutant under low temperature compared to WT. Transmission electron microscope observation revealed that chloroplasts were defectively developed in the albino ltal leaves, which lacked of well-stacked granum and contained less stroma lamellae. These results suggested that the ltal mutation may delay the light-induced thylakoid assembly under low temperature. Genetic analysis indicated that the albino phenotype was controlled by a single recessive locus. Through map-based approach, we finally located the Ltal gene to a region of 40.3 kb on the short arm of chromosome 11. There are 8 predicted open reading frames (ORFs) in this region and two of them were deleted in ltal genome compared with the WT genome. The further characterization of the Ltal gene would provide a good approach to uncover the novel molecular mechanisms involved in chloroplast development under low temperature stress.展开更多
基金This work was funded by the National Natural Science Foundation of China(32172597 and 31830067)the Chongqing Talents of Exceptional Young Talents Project,China(CQYC202005097,cstc2021ycjh-bgzxm0204,and cstc2021jcyj-bshX0002)+2 种基金the China Agriculture Research System of MOF and MARA(CARS-12)the 111 Project,China(B12006)the Germplasm Creation Special Program of Southwest University,China。
文摘Enhancing photosynthetic efficiency is a major goal for improving crop yields under agricultural field conditions and is associated with chloroplast biosynthesis and development.In this study,we demonstrate that Golden2-like 1a(BnGLK1a)plays an important role in regulating chloroplast development and photosynthetic efficiency.Overexpressing BnGLK1a resulted in significant increases in chlorophyll content,the number of thylakoid membrane layers and photosynthetic efficiency in Brassica napus,while knocking down BnGLK1a transcript levels through RNA interference(RNAi)had the opposite effects.A yeast two-hybrid screen revealed that BnGLK1a interacts with the abscisic acid receptor PYRABACTIN RESISTANCE 1-LIKE 1-2(BnPYL1-2)and CONSTITUTIVE PHOTOMORPHOGENIC 9 SIGNALOSOME 5A subunit(BnCSN5A),which play essential roles in regulating chloroplast development and photosynthesis.Consistent with this,BnGLK1a-RNAi lines of B.napus display hypersensitivity to the abscisic acid(ABA)response.Importantly,overexpression of BnGLK1a resulted in a 10%increase in thousand-seed weight,whereas seeds from BnGLK1a-RNAi lines were 16%lighter than wild type.We propose that BnGLK1a could be a potential target in breeding for improving rapeseed productivity.Our results not only provide insights into the mechanisms of BnGLK1a function,but also offer a potential approach for improving the productivity of Brassica species.
基金supported by the Program for Subsidized Project of Suzhou Academy of Agricultural Sciences,China(20028)the Science and Technology Foundation of Suzhou(SNG2020048)+3 种基金the Huaishang Talents,China,the National Natural Science Foundation of China(32070345)the Huai’an Academy of Agricultural Sciences Initiation and Development of Scientific Research Fund for High-level Introduced Talents,China(0062019016B)the Six Talents Summit Project of Jiangsu Province,China(NY-129)the Natural Science Foundation of Jiangsu Province,China(BK20190239 and BK20180107)。
文摘Plant chlorophyll biosynthesis and chloroplast development are two complex processes that are regulated by exogenous and endogenous factors. In this study, we identified OsDXR, a gene encoding a reductoisomerase that positively regulates chlorophyll biosynthesis and chloroplast development in rice. OsDXR knock-out lines displayed the albino phenotype and could not complete the whole life cycle process. OsDXR was highly expressed in rice leaves, and subcellular localization indicated that OsDXR is a chloroplast protein. Many genes involved in chlorophyll biosynthesis and chloroplast development were differentially expressed in the OsDXR knock-out lines compared to the wild type.Moreover, we found that the RNA editing efficiencies of ndhA-1019 and rpl2-1 were significantly reduced in the OsDXR knock-out lines. Furthermore, OsDXR interacted with the RNA editing factor OsMORF1 in a yeast two-hybrid screen and bimolecular fluorescence complementation assay. Finally, disruption of the plastidial 2-C-methyl-derythritol-4-phosphate pathway resulted in defects in chloroplast development and the RNA editing of chloroplast genes.
基金supported by the National Natural Science Foundation of China(Grant Nos.32201516,91954202)the Youth Top-notch Talent Program of Hebei Education Department(BJK2022028)+1 种基金National Training Program of Innovation and Entrepreneurship for Undergraduates(Grant Nos.S202110022037,G202010022075)the funding of Hebei North University(XJ2021013)。
文摘The nuclear-encoded factors and the photosynthetic apparatus have been studied extensively during chloroplast biogenesis.However,many questions regarding these processes remain unanswered,particularly in perennial woody plants.As a model material of woody plants,poplar not only has very significant value of research,but also possesses economic and ecological properties.This study reports the Populus trichocarpa DJ-1C(PtrDJ1C)factor,encoded by a nuclear gene,and a member of the DJ-1 superfamily.PtrDJ1C knock-out with the CRISPR/Cas9 system resulted in different albino phenotypes.Chlorophyll fluorescence and immunoblot analyses showed that the levels of photosynthetic complex proteins decreased significantly.Moreover,the transcript level of plastid-encoded RNA polymerase-dependent genes and the splicing efficiency of several introns were affected in the mutant line.Furthermore,rRNA accumulation was abnormal,leading to developmental defects in chloroplasts and affecting lignin accumulation.We concluded that the PtrDJ1C protein is essential for early chloroplast development and lignin deposition in poplar.
基金funded by the Central Public-Interest Scientific Institution Basal Research Fund,China(CPSIBRF-CNRRI-202111 and CPSIBRF-CNRRI-202110)the Agricultural Science and Technology Innovation Program,Chinese Academy of Agricultural Sciences(ASTIP)+1 种基金the Project of State Key Laboratory of Rice Biology,China(2020ZZKT10205)the Key Research and Development Project of China Rice Research Institute(CNRRI-2020-01)。
文摘Photosynthesis occurs mainly in chloroplasts,whose development is regulated by proteins encoded by nuclear genes.Among them,pentapeptide repeat(PPR)proteins participate in organelle RNA editing.Although there are more than 450 members of the PPR protein family in rice,only a few affect RNA editing in rice chloroplasts.Gene editing technology has created new rice germplasm and mutants,which could be used for rice breeding and gene function study.This study evaluated the functions of OsPPR9 in chloroplast RNA editing in rice.The osppr9 mutants were obtained by CRISPR/Cas9,which showed yellowing leaves and a lethal phenotype,with suppressed expression of genes associated with chloroplast development and accumulation of photosynthetic-related proteins.In addition,loss of OsPPR9 protein function reduces the editing efficiency of rps8-C182,rpoC2-C4106,rps14-C80,and ndhB-C611 RNA editing sites,which affects chloroplast growth and development in rice.Our data showed that OsPPR9 is highly expressed in rice leaves and encodes a DYW-PPR protein localized in chloroplasts.Besides,the OsPPR9 protein was shown to interact with OsMORF2 and OsMORF9.Together,our findings provide insights into the role of the PPR protein in regulating chloroplast development in rice.
基金supported by the Key Laboratory of Biology, GeneticsBreeding of Japonica Rice in the Mid-lower Yangtze River, Ministry of Agriculture, China+5 种基金Jiangsu Plant Gene Engineering Research CenterJiangsu Collaborative Innovation Center for Modern Crop ProductionThis research was also supported by grants from the National Natural Science Foundation (92035301)Jiangsu Science and Technology Development Program (BE2021360)Jiangsu Agricultural Science and Technology Innovation Fund Project (SCX (19)1079)the Fundamental Research Funds for the Central Universities (JCQY201902)。
文摘Pentatricopeptide repeat(PPR) proteins function in post-transcriptional regulation of organellar gene expression. Although several PPR proteins are known to function in chloroplast development in rice(Oryza sativa), the detailed molecular functions of many PPR proteins remain unclear.Here, we characterized a rice young leaf white stripe(ylws) mutant, which has defective chloroplast development during early seedling growth.Map-based cloning revealed that YLWS encodes a novel P-type chloroplast-targeted PPR protein with 11 PPR motifs. Further expression analyses showed that many nuclear-and plastid-encoded genes in the ylws mutant were significantly changed at the RNA and protein levels. The ylws mutant was impaired in chloroplast ribosome biogenesis and chloroplast development under low-temperature conditions. The ylws mutation causes defects in the splicing of atpF, ndhA, rpl2,and rps12, and editing of ndhA, ndhB, and rps14transcripts. YLWS directly binds to specific sites in the atpF, ndhA, and rpl2 pre-mRNAs. Our results suggest that YLWS participates in chloroplast RNA group II intron splicing and plays an important role in chloroplast development during early leaf development.
基金supported by the General Research Fund(CUHK codes 14121915,14148916,and 14104521)the Area of Excellence Scheme(AoE/M-403/16 and AoE/M-05/12)of the Research Grants Council(RGC)of Hong Kong+1 种基金the National Natural Science Foundation of China(NSFC)-RGC Joint Scheme(N_CUHK452/17)direct grants from the Chinese University of Hong Kong(CUHK).
文摘The cytochrome b_(6f)(Cyt b_(6f))complex is a multisubunit protein complex in chloroplast thylakoid membranes required for photosynthetic electron transport.Here we report the isolation and characterization of the new tiny albino 1(nta1)mutant in Arabidopsis,which has severe defects in Cyt b_(6f) accumulation and chloroplast development.Gene cloning revealed that the nta1 phenotype was caused by disruption of a single nuclear gene,NTA1,which encodes an integral thylakoid membrane protein conserved across green algae and plants.Overexpression of NTA1 completely rescued the nta1 phenotype,and knockout of NTA1 in wild-type plants recapitulated the mutant phenotype.Loss of NTA1 function severely impaired the accumulation of multiprotein complexes related to photosynthesis in thylakoid membranes,particularly the components of Cyt b_(6f).NTA1 was shown to directly interact with four subunits(Cyt b6/PetB,PetD,PetG,and PetN)of Cyt b_(6f) through the DUF1279 domain and C-terminal sequence to mediate their assembly.Taken together,our results identify NTA1 as a new and key regulator of chloroplast development that plays essential roles in assembly of the Cyt b_(6f) complex by interacting with multiple Cyt b_(6f) subunits.
基金supported by Natural Science Foundation of China (no. 30971552)Shanghai Municipal Education Commission of China (no. 14YZ076)+2 种基金Shanghai Municipal Science and Technology Commission of China (10DZ2271800, 12ZR1422000)Leading Academic Discipline Project of Shanghai Municipal Education Commission (no. J50401)the Food Safety and Nutrition Program of Shanghai Normal University (DXL123)
文摘Pentatricopeptide repeat (PPR) proteins, charac- terized by tandem arrays of a 35 amino acid motif, have been suggested to play central and broad roles in modulating the expression of organelle genes in plants. However, the molecular mechanisms of most rice PPR genes remains unclear. In this paper, we isolated and characterized a temperature-conditional virescent mutant, OsV4, in rice (Oryza sativa cultivar Jiahual (WT, japonica rice variety)). The mutant displays albino phenotype and abnormal chloroplasts at the three leaf stage, which gradually turns green after the four leaf stage at a low temperature (20℃). But the mutant always develops green leaves and well-developed chloroplasts at a high temperature (32℃). Genetic and molecular analyses uncovered that OsV4 encodes a novel chloroplast-targeted PPR protein including four PPR motifs. Further investigations show that the mutant phenotype is associated with changes in chlorophyll content and chloroplast development. The OsV4 transcripts only accumulate to high levels in young leaves, indicating that its expression is tissue-specific. In addition, transcript levels of some ribosomal components and plastid- encoded polymerase-dependent genes are dramatically re- duced in the albino mutants grown at 20℃. These findings suggest that OsV4 plays an important role during early chloroplast development under cold stress in rice.
文摘Although the multiple organellar RNA editing factors (MORFs) in the plastids of Arabidopsis thaliana have been extensively studied, molecular details underlying how MORFs affect plant development in other species, particularly in rice, remain largely unknown. Here we describe the characterization of wspl, a rice mutant with white-stripe leaves and panicles. Notably, wspl exhibited nearly white immature panicles at the heading stage. Transmission electron microscopy analysis and chlorophyll content measurement re- veale i a chloroplast developmental defect and reduced chlorophyll accumulation in wspl. Positional cloning of WSP1 found a point mutation in OsO4g51280, whose putative product shares high sequence similarity with MORF proteins. Complementation experiments demonstrated that WSP1 was responsible for the variegated phenotypes of wspl. WSP1 is localized to chloroplasts and the point mutation in wspl affected the editing of multiple organellar RNA sites. Owing to the defect in plastid RNA editing, chloroplast ribosome biogenesis and ndhA splicing were also impaired in wspl, which may affect normal chloroplast development in the leaves and panicles at the heading stage. Together, our results demonstrate the importance of rice WSP1 protein in chloroplast development and broaden our knowledge about MORF family members in rice.
基金supported by grants from the National Natural Science Foundation of China (31271800 and 31571742)the Zhejiang Provincial Natural Science Foundation of China (Z3110509)+1 种基金the National High-tech R&D Program of China (863 Program) (2012AA10A302-6)the Transgenic Project (2014ZX08010-002)
文摘Functional chloroplast generation depends on the precise coordination of gene expression between the plastid and the nucleus and is essential for plant growth and development. In this study, a rice(Oryza sativa) mutant that exhibited albino and seedling-lethal phenotypes was isolated from a60Co-irradiated rice population. The mutant gene was identified as an ortholog of the Arabidopsis plastid transcriptionally active chromosome protein 2(p TAC2) gene, and the mutant strain was designated osptac2. Sequence and transcription analyses showed that Osp TAC2 encodes a putative chloroplast protein consisting of 10 pentratricopeptide repeat(PPR) domains and a C-terminal small Mut S-related(SMR) domain. Cytological observations via microscopy showed that the Osp TAC2-green fluorescent fusion protein is localized in the chloroplasts. Transmission electron microscopy revealed that the chloroplast of the osptac2 mutant lacks an organized thylakoid membrane. The transcript levels of all investigated PEP(plastid-encoded RNA polymerase)-dependent genes were dramatically reduced in the osptac2 mutant, whereas the transcript levels of NEP(nuclear-encoded polymerase)-dependent genes were increased. These results suggest that Osp TAC2 plays a critical role in chloroplast development and indicate that the molecular function of the Osp TAC2 gene is conserved in rice and Arabidopsis.
文摘Plants contain various factors that transiently interact with subunits or intermediates of the thylakoid multiprotein complexes, promoting their stable association and integration. Hence, assembly factors are essential for chloroplast development and the transition from heterotrophic to phototrophic growth. Snowy cotyledon 2 (SCO2) is a DNAJ-like protein involved in thylakoid membrane biogenesis and interacts with the light-harvesting chlorophyll-binding protein LHCBI. In Arabidopsis thaliana, SCO2 function was previ- ously reported to be restricted to cotyledons. Here we show that disruption of SC02 in Lotus japonicus results not only in paler cotyledons but also in variegated true leaves. Furthermore, smaller and pale- green true leaves can also be observed in A. thaliana sco2 (atsco2) mutants under short-day conditions. In both species, SCO2 is required for proper accumulation of PSlI-LHCll complexes. In contrast to other variegated mutants, inhibition of chloroplastic translation strongly affects L. japonicus sco2 mutant devel- opment and fails to suppress their variegated phenotype. Moreover, inactivation of the suppressor of variegation AtClpR1 in the atsco2 background results in an additive double-mutant phenotype with variegated true leaves. Taken together, our results indicate that SCO2 plays a distinct role in PSll assembly or repair and constitutes a novel factor involved in leaf variegation.
基金supported by the grant from the Ministry of Science and Technology of China (No. 2012AA10A302-2)
文摘Mutants with abnormal leaf coloration are good genetic materials for understanding the mechanism of chloroplast development and chlorophyll biosynthesis. In this study, a rice mutant st2 (stripe2) with stripe leaves was identified from the "y-ray irradiated mutant pool. The st2 mutant exhibited decreased accumulation of chlorophyll and aberrant chloroplasts. Genetic analysis indicated that the st2 mutant was controlled by a single recessive locus. The ST2 gene was finely confined to a 27-kb region on chromosome 1 by the map-based cloning strategy and a 5-bp deletion in Os01g0765000 was identified by sequence analysis. The deletion happened in the joint of exon 3 and intron 3 and led to new spliced products of mRNA. Genetic comptementation confirmed that Os01g0765000 is the ST2 gene. We found that the ST2 gene was expressed ubiquitously. Subcellular localization assay showed that the ST2 protein was located in mitochondria. ST2 belongs to the cytidine deaminase-like family and possibly functions as the dCMP deaminase, which catalyzes the formation of dUMP from dCMP by deamination. Additionally, exogenous application of dUMP could partially rescue the st2 phenotype. Therefore, our study identified a putative dCMP deaminase as a novel regulator in chloroplast development for the first time.
基金This work was supported by the Natural Science Foundation of Zhejiang province(LR20C13002)the special support plan for high level talents in Zhejiang Province(2019R52032)Agricultural Sciences and Technologies Innovation Program of the Chinese Academy of Agricultural Sciences.
文摘Pentatricopeptide repeat(PPR)proteins play important roles in the post-transcriptional modification of organellar RNAs in plants.However,the function of most PPR proteins remains unknown.Here,we characterized the rice(Oryza sativa L.)chlorophyll deficient 4(cde4)mutant which exhibits an albino phenotype during early leaf development,with decreased chlorophyll contents and abnormal chloroplasts at low-temperature(20℃).Positional cloning revealed that CDE4 encodes a P-type PPR protein localized in chloroplasts.In the cde4 mutant,plastid-encoded polymerase(PEP)-dependent transcript levels were significantly reduced,but transcript levels of nuclear-encoded genes were increased compared to wild-type plants at 20℃.CDE4 directly binds to the transcripts of the chloroplast genes rpl2,ndhA,and ndhB.Intron splicing of these transcripts was defective in the cde4 mutant at 20℃,but was normal at 32℃.Moreover,CDE4 interacts with the guanylate kinase VIRESCENT 2(V2);overexpression of V2 enhanced CDE4 protein stability,thereby rescuing the cde4 phenotype at 20℃.Our results suggest that CDE4 participates in plastid RNA splicing and plays an important role in rice chloroplast development under lowtemperature conditions.
基金supported by National Natural Science Foundation of China (31371606, 31601284, 31661143006)The Transgenic Plant Research and Commercialization Project of the Ministry of Agriculture of China (2016ZX08001003-002)+2 种基金Zhejiang Province Outstanding Youth Fund (LR16C130001)The Collaborative Innovation Project of the Chinese Academy of Agricultural Sciences (Y2016XT05)State Key Laboratory of Rice Biology Research Project (2017ZZKT10103)
文摘Chloroplast genes are transcribed by the plastidencoded RNA polymerase(PEP) or nucleus-encoded RNA polymerase. FRUCTOKINASE-LIKE PROTEINS(FLNs) are phosphofructokinase-B(Pfk B)-type carbohydrate kinases that act as part of the PEP complex; however, the molecular mechanisms underlying FLN activity in rice remain elusive.Previously, we identified and characterized a heat-stress sensitive albino(hsa_1) mutant in rice. Map-based cloning revealed that HSA_1 encodes a putative OsFLN_2. Here, we further demonstrated that knockdown or knockout of the OsFLN_1, a close homolog of HSA_1/OsFLN_2, considerably inhibits chloroplast biogenesis and the fln_1 knockout mutants, created by clustered regularly interspaced short palindromic repeats(CRISPR) and CRISPR-associate protein_9, exhibit severe albino phenotype and seedling lethality. Moreover, OsFLN_1 localizes to the chloroplast.Yeast two-hybrid, pull-down and bimolecular fluorescencecomplementation experiments revealed that OsFLN_1 and HSA_1/OsFLN_2 interact with THIOREDOXINZ(OsTRXz) to regulate chloroplast development. In agreement with this,knockout of OsTRXz resulted in a similar albino and seedling lethality phenotype to that of the fln_1 mutants. Quantitative reverse transcription polymerase chain reaction and immunoblot analysis revealed that the transcription and translation of PEP-dependent genes were strongly inhibited in fln_1 and trxz mutants, indicating that loss of OsFLN_1, HSA_1/OsFLN_2, or OsTRXz function perturbs the stability of the transcriptionally active chromosome complex and PEP activity. These results show that OsFLN_1 and HSA_1/OsFLN_2 contribute to chloroplast biogenesis and plant growth.
基金supported by the the“JBGS”Project of Seed Industry Revitalization in Jiangsu Province,China(JBGS[2021]018)the Jiangsu Agricultural Innovation of New Cultivars,China(PZCZ201720)the Open Project Program of Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement,China(K2020030)。
文摘Leaf color mutants in higher plants are considered to be ideal materials for studying the chlorophyll biosynthesis,photosynthesis mechanism and chloroplast development.Herein,we identified a spontaneous mutant,yc412,in cultivated cucumber that exhibited yellow cotyledons.The yellow-lethal mutant was diagnosed with an abnormal chloroplast ultrastructure,and reduced photosynthetic capacity and pigment content.Through bulked segregant analysis-based whole-genome sequencing and fine genetic mapping,we narrowed the yellow cotyledons (yc) locus to a 96.8 kb interval on chromosome 3.By resequencing and molecular cloning,we showed that Csyc is a potential candidate gene,which encodes a yellow stripe-like (YSL) transporter.The T to C mutation in the promoter region of Csyc caused the yellow cotyledon phenotype in yc412.Compared to YZU027A (WT),the expression of Csyc was significantly downregulated in the cotyledons of yc412.Silencing of Csyc in cucumber via virus-induced gene silencing resulted in chlorotic leaves,mainly by suppressing the chlorophyll content.Furthermore,a comparative transcriptome analysis revealed that chloroplast-related genes and chlorophyll biosynthesis genes were significantly downregulated in yc412 cotyledons.Our results provide new insights into the molecular function of the YSL transporter in plant chloroplast development and chlorophyll synthesis.
基金supported by the National Natural Science Foundation of China(31801335)Training Program for Excellent Young Innovators of Changsha(kq1802034)Department of Science and Technology in Hunan Province(2019RS2047).
文摘Plant architecture strongly influences rice grain yield.We report the cloning and characterization of the LTA1 gene,which simultaneously controls tiller angle and yield of rice.LTA1 encodes a chloroplastlocalized protein with a conserved YbaB DNA-binding domain,and is highly expressed in photosynthetic tissues including leaves and leaf sheaths.Disrupting the function of LTA1 leads to large tiller angle and yield reduction of rice.LTA1 affects the gravity response by mediating the distribution of endogenous auxin,thereby regulating the tiller angle.An lta1 mutant showed abnormal chloroplast development and decreased chlorophyll content and photosynthetic rate,in turn leading to reduction of rice yield.Our findings shed light on the genetic basis of tiller angle and provide a potential gene resource for the improvement of plant architecture and rice yield.
基金supported by the National Key Research and Development Program of China (2016YFD0102104)Platform for Mutation Breeding by Radiation of Sichuan (2016NZ0106)Applied Basic Research Program of Sichuan Provincial Science and Technology Department (2020YJ0249)。
文摘A nuclear-encoded sigma(σ) factor is essential for the transcriptional regulation of plant chloroplastencoded genes. Five putative maize r factors have been identified by database searches, but their functions are unknown. We report a maize leaf color mutant etiolated/albino leaf 1(eal1) that was derived from space mutation breeding. The eal1 mutant displays etiolated or albino leaves that then gradually turn to normal green at the seedling stage. The changes in eal1 leaf color are associated with changes in photosynthetic pigment content and chloroplast development. Map-based cloning revealed that a single amino-acid deletion changing Val_(480)-Val_(481)-Val_(482) to Val_(480)-Val_(481), in the C-terminal domain σ_(4) of the putative σ factor ZmSig2A, is responsible for the eal1 mutation. In comparison with the expression level of the wild-type(WT) allele ZmSig2A^(+) in WT plants, much higher expression of the mutant allele ZmSig2A^(⊿V) in eal1 plants was detected before the eal1 plants turned to normal green. ZmSig2A shows the highest similarity to rice OsSig2A and Arabidopsis SIG2. Ectopic expression of ZmSig2A^(+) or ZmSig2A^(⊿V) driven by the cauliflower mosaic virus 35 S promoter rescued the pale green leaf of the sig2 mutant, but ectopic expression of ZmSig2A^(⊿V) driven by the SIG2 promoter did not. We propose that the Val deletion generated a new weak allele of ZmSig2A that cannot completely abolish the ZmSig2A function. Some genes involved in chloroplast development and photosynthesis-associated nuclear genes showed significant expression differences between eal1 and WT plants. We conclude that ZmSig2A encoding a r factor is essential for maize chloroplast development. The eal1 mutant with a weak allele of ZmSig2A represents a valuable genetic resource for investigating the regulation of ZmSig2A-mediated chloroplast development in maize.The eal1 mutation may be useful as a marker for early identification and elimination of false hybrids or transgene transmission in the application of genetic male sterility to commercial hybrid seed production.
基金financially supported by grants from the National Natural Science Foundation of China(Nos.31625004 and 31872653)the 111 Project(B14027)。
文摘Chloroplasts are important for plant growth and development.RNA editing in chloroplast converts cytidines(Cs)to uridine s(Us)at specific transcript positions and provides a correction mechanism to restore conserved codons or creates start or stop codons.However,the underlined molecular mechanism is not yet fully unders tood.In the present study,we identi fied a thermo-sensi tive mutantin leaf color 1(tst1)and found that TSL1 is allelic to DELAYED GREENING 1(DG1).The mis sense mutation of DG1 in tsl1 mutant confers a high temperature sensitivity and impaired chloroplast development at an elevated ambient temperature in Arabidopsis.Subsequent analysis showed that chloroplast RNA editing at seve ral sites including accD-2568,ndhD-2,and petL-5 is impaired in tsl1 mutant plants grown at an elevated temperature.DG1 interacts with MORF2 and other proteins such as DYW1 and DYW2 involved in chloroplast RNA editing.In vitro RNA electrophoretic mobility shift assay demonstrated that DG1 binds to RNA targets such as accD,ndhD,and petL.Thus,our results revealed that DG1 is important for maintaining chloroplast mRNA editing in Arabidopsis.
基金supported by the grants from the National Basic Research Program of China(No.2009CB119000)the Ministry of Agriculture of China for Transgenic Research (Nos.2011ZX08009-003,2011ZX08001-005)the National Science Foundation of China(Nos.31000094,30970246, 31100188 and 31161130533)
文摘Albino mutants are useful genetic resource for studying chlorophyll biosynthesis and chloroplast development and cloning genes involved in these processes in plants. Here we report a novel rice mutant low temperature albino I (ltal) that showed albino leaves before 4-leaf stage when grown under temperature lower than 20℃, but developed normal green leaves under temperature higher than 24℃ or similar morphological phenotypes in dark as did the wild-type (WT). Our analysis showed that the contents of chlorophylls and chlo- rophyll precursors were remarkably decreased in the Ital mutant under low temperature compared to WT. Transmission electron microscope observation revealed that chloroplasts were defectively developed in the albino ltal leaves, which lacked of well-stacked granum and contained less stroma lamellae. These results suggested that the ltal mutation may delay the light-induced thylakoid assembly under low temperature. Genetic analysis indicated that the albino phenotype was controlled by a single recessive locus. Through map-based approach, we finally located the Ltal gene to a region of 40.3 kb on the short arm of chromosome 11. There are 8 predicted open reading frames (ORFs) in this region and two of them were deleted in ltal genome compared with the WT genome. The further characterization of the Ltal gene would provide a good approach to uncover the novel molecular mechanisms involved in chloroplast development under low temperature stress.