Water is the most abundant molecule in almost all living organisms. Aquaporins are channel proteins that play critical roles in controlling the water content of cells. Here, we report the identification of an AP2/EREB...Water is the most abundant molecule in almost all living organisms. Aquaporins are channel proteins that play critical roles in controlling the water content of cells. Here, we report the identification of an AP2/EREBP family transcription factor in Arabidopsis thaliana, TRANSLUCENT GREEN （TG）, whose overexpression in transgenic plants gave enhanced drought tolerance and vitrified leaves. TG protein is localized in the nucleus, binds DRE and GCC elements in vitro, and acts as a transcriptional activator in yeast cells. Microarray analysis revealed a total of 330 genes regulated by TG, among which five genes encode aquaporins. A transient expression assay showed that TG directly binds to the promoters of three aquaporin genes, such as AtTIP1;1, AtTIP2;3, and AtPIP2;2, indicating that TG directly regulates the expression of these genes. Moreover, overexpression of AtTIP1;1 resulted in vitrified phenotypes in transgenic Arabidopsis plants, similar to those observed in TG overexpression lines. Water injection into wild-type leaves recapitulated the vitrified leaf phenotypes, which was reversed by cutting off the water supply from vascular bundles. Taken together, our data support that TG controls water balance in Arabidopsis through directly activating the expression of aquaporin genes.展开更多
Complex I （the NADH：ubiquinone oxidoreductase） of the mitochondrial respiratory chain is a complicated, multi-subunit, membrane- bound assembly and contains more than 40 different proteins in higher plants. In this...Complex I （the NADH：ubiquinone oxidoreductase） of the mitochondrial respiratory chain is a complicated, multi-subunit, membrane- bound assembly and contains more than 40 different proteins in higher plants. In this paper, we characterize the Arabidopsis homologue （designated as AtCIB22） of the B22 subunit of eukaryotic mitochondriai Complex I. AtCIB22 is a single-copy gene and is highly con- served throughout eukaryotes. AtCIB22 protein is located in mitochondria and the AtC1B22 gene is widely expressed in different tissues. Mutant Arabidopsis plants with a disrupted AtC1B22 gene display pleiotropic phenotypes including shorter roots, smaller plants and de- layed flowering. Stress analysis indicates that the AtC1B22 mutants＇ seed germination and early seedling growth are severely inhibited by sucrose deprivation stress but more tolerant to ethanol stress. Molecular analysis reveals that in moderate knockdown AtCIB22 mutants, genes including cell redox proteins and stress related proteins are significantly up-regulated, and that in severe knockdown AtCIB22 mu- tants, the alternative respiratory pathways including NDA1, NDB2, AOXla and AtPUMP1 are remarkably elevated. These data demon- strate that AtCIB22 is essential for plant development and mitochondrial electron transport chains in Arabidopsis. Our findings also en- hance our understanding about the physiological role of Complex I in plants.展开更多
In plants,one of the most common modifications of secondary metabolites is methylation catalyzed by various methyltransferases. Recently,a new class of methyltransferases,the SABATH family of methyltransferases,was fo...In plants,one of the most common modifications of secondary metabolites is methylation catalyzed by various methyltransferases. Recently,a new class of methyltransferases,the SABATH family of methyltransferases,was found to modify phytohormones and other small molecules.The SABATH methyltransferases share little sequence similarity with other well characterized methyltransferases.Arabidopsis has 24 members of the SABATH methyltransferase genes,and a subset of them has been shown to catalyze the formation of methyl esters with phytohormones and other small molecules.Physiological and genetic analyses show that methylation of phytohormones plays important roles in regulating various biological processes in plants,including stress responses,leaf development,and seed maturation/germination.In this review,we focus on phytohormone methylation by the SABATH family methyltransferases and the implication of these modifications in plant development.展开更多
The Mediator complex is an important component of the eukaryotic transcriptional machinery. As an essential link between transcription factors and RNA polymerase II, the Mediator complex transduces diverse signals to ...The Mediator complex is an important component of the eukaryotic transcriptional machinery. As an essential link between transcription factors and RNA polymerase II, the Mediator complex transduces diverse signals to genes involved in different pathways. The plant Mediator complex was recently purified and comprises conserved and specific subunits. It functions in concert with transcription factors to modulate various responses. In this review, we summarize the recent advances in understanding the plant Mediator complex and its diverse roles in plant growth, development, defense, non-coding RNA production, response to abiotic stresses, flowering, genomic stability and metabolic homeostasis. In addition, the transcription factors interacting with the Mediator complex are also highlighted.展开更多
In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than doubl...In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than double fertilization, can trigger ovule enlargement. However, it remains unclear whether the signal（s） to trigger the initiation of ovule enlargement are from the sperm cells or fromthe pollen tubes. Recently, we identified a mutant dropl- drop2-, which produces pollen tubes with no sperm cells. Taking advantage of this special genetic material, we conducted pollination assays, and found that the ovules pollinated with dropl- drop2- pollen could initiate the enlargement and exhibited significant enlarged sizes at 36h after pollination in comparison with those unpollinated ovules. However, the sizes of the ovules pollinated with drops- drop2- pollen are significantly smaller than those of the ovules pollinated with wildtype pollen. These results demonstrate that the pollen tube, rather than the sperm cells, release the signal to trigger the initiation of ovule enlargement, and that double fertilization is required for further enlargement of the seeds.展开更多
The activities of transcription factors （TFs） require interactions with specific DNA sequences and other reg- ulatory proteins. To detect such interactions in Arabidopsis, we developed a high-throughput screening sy...The activities of transcription factors （TFs） require interactions with specific DNA sequences and other reg- ulatory proteins. To detect such interactions in Arabidopsis, we developed a high-throughput screening system with a Gateway-compatible Gal4-AD-TF library of 1589 Arabidopsis TFs, which can be easily screened by mating-based yeast-one-hybrid （YIH） and yeast-two-hybrid （Y2H） methods. The efficiency of the system was validated by examining two well-characterized TF-DNA and TF-protein interactions： the CHE-CCA1 promoter interaction by YIH and NPR1-TGAs interactions by Y2H. We used this system to identify eight TFs that interact with a Mediator subunit, Med25, a key reg- ulator in JA signaling. We identified five TFs that interacted with the GCC-box cis-element in the promoter of PDF1.2, a downstream gene of Med25. We found that three of these TFs, all from the AP2-EREBP family, interact directly both with Med25 and the GCC-box of PDF1.2, suggesting that Med25 regulates PDF1.2 expression through these three TFs. These results demonstrate that this high-throughput Y1H/Y2H screening system is an efficient tool for studying transcrip- tional regulation networks in Arabidopsis. This system will be available for other Arabidopsis researchers, and thus it provides a vital resource for the Arabidopsis community.展开更多
VPS 15 protein is a component of the phosphatidylinositol 3-kinase complex which plays a pivotal role in the development of yeast and mammalian cells. The knowledge about the function of its homologue in plants remain...VPS 15 protein is a component of the phosphatidylinositol 3-kinase complex which plays a pivotal role in the development of yeast and mammalian cells. The knowledge about the function of its homologue in plants remains limited. Here we report that AtVPS15, a homologue of yeast VPS15p in Arabidopsis, plays an essential role in pollen germination. Homozygous T-DNA insertion mutants of AtVPS15 could not be obtained from the progenies of self-pollinated heterozygous mutants. Reciprocal crosses between atvps15 mutants and wild-type Arabidopsis revealed that the T-DNA insertion was not able to be transmitted by male gametophytes. DAPI staining, Alexander＇s stain and scanning electron microscopic analysis showed that atvps15 heterozygous plants produced pollen grains that were morphologically indistinguishable from wild-type pollen, whereas in vitro germination experiments revealed that germination of the pollen grains was defective. GUS staining analysis of transgenic plants expressing the GUS reporter gene driven by the AtVPS15 promoter showed that AtVPS15 was mainly expressed in pollen grains. Finally, DUALmembrane yeast two-hybrid analysis demonstrated that AtVPS15 might interact directly with AtVPS34. These results suggest that AtVPS15 is very important for pollen germination, possibly through modulation of the activity of PI3-kinase.展开更多
In flowering plants,the two sperm cells are passive cargo transported into the ovule by pollen tubes (Zhang et al.,2017).Therefore,the precise guidance of pollen tubes is critical for successful double fertilization (...In flowering plants,the two sperm cells are passive cargo transported into the ovule by pollen tubes (Zhang et al.,2017).Therefore,the precise guidance of pollen tubes is critical for successful double fertilization (Dresselhaus and Franklin-Tong,2013).A series of male-female interactions are required to guarantee the spatiotemporal regulation of pollen tube guidance because during growth,pollen tubes continuously interact with different female tissues (Zhong et al.,2017;Zhong and Qu,2019).In the past two decades,there has been tremendous progress in elucidating the molecular mechanisms of pollen tube guidance regulation,mostly using Arabidopsis thaliana as a model system (Johnson et al.,2019).展开更多
In plants, RNA editing is a post-transcriptional process that changes specific cytidine to uridine in both mitochondria and plastids. Most pentatricopeptide repeat（PPR） proteins are involved in organelle RNA editing...In plants, RNA editing is a post-transcriptional process that changes specific cytidine to uridine in both mitochondria and plastids. Most pentatricopeptide repeat（PPR） proteins are involved in organelle RNA editing by recognizing specific RNA sequences. We here report the functional characterization of a PPR protein from the DYW subclass, Baili Xi（BLX）, which contains five PPR motifs and a DYW domain. BLX is essential for early seed development, as plants lacking the BLX gene was embryo lethal and the endosperm failed to initiate cellularization. BLX was highly expressed in the embryo and endosperm, and the BLX protein was specifically localized in mitochondria, which is essential for BLX function. We found that BLX was required for the efficient editing of 36 editing sites in mitochondria. Moreover, BLX was involved in the splicing regulation of the fourth intron of nad1 and the first intron of nad2. The loss of BLX function impaired the mitochondrial function and increased the reactive oxygen species（ROS） level. Genetic complementation with truncated variants of BLX revealed that, in addition to the DYW domain, only the fifth PPR motif was essential for BLX function. The upstream sequences of the BLX-targeted editing sites are not conserved, suggesting that BLX serves as a novel and major mitochondrial editing factor（MEF） via a new non-RNA-interacting manner. This finding provides new insights into how a DYW-type PPR protein with fewer PPR motifs regulates RNA editing in plants.展开更多
The signaling pathway of the gaseous hormone ethylene is involved in plant reproduction,growth,devel-opment,and stress responses.During reproduction,the two synergid cells of the angiosperm female gametophyte both und...The signaling pathway of the gaseous hormone ethylene is involved in plant reproduction,growth,devel-opment,and stress responses.During reproduction,the two synergid cells of the angiosperm female gametophyte both undergo programmed cell death(PCD)/degeneration but in a different manner:PCD/degeneration of one synergid facilitates pollen tube rupture and thereby the release of sperm cells,while PCD/degeneration of the other synergid blocks supernumerary pollen tubes.Ethylene signaling was postu-lated to participate in some of the synergid cell functions,such as pollen tube attraction and the induction of PCD/degeneration.However,ethylene-mediated induction of synergid PCD/degeneration and the role of ethylene itself have not been firmly established.Here,we employed the CRISPR/Cas9 technology to knock out the five ethylene-biosynthesis 1-aminocyclopropane-1-carboxylic acid oxidase(ACO)genes and created Arabidopsis mutants free of ethylene production.The ethylene-free mutant plants showed normal triple responses when treated with ethylene rather than 1-aminocyclopropane-1-carboxylic acid,but had increased lateral root density and enlarged petal sizes,which are typical phenotypes of mutants defective in ethylene signaling.Using these ethylene-free plants,we further demonstrated that production of ethylene is not necessarily required to trigger PCD/degeneration of the two synergid cells,but certain com-ponents of ethylene signaling including transcription factors ETHYLENE-INSENSITIVE 3(EIN3)and EIN3-LIKE 1(EIL1)are necessary for the death of the persistent synergid cell.展开更多
基金The work was supported by the National Natural Science Foundation of China(Grant No.30470172 and 30221120261)the National Special Projects for R&D of Transgenic Plants(J99-A-001).
基金Acknowledgments The authors thank Dr Liying Du （Peking University, China） for technical help on the flow cytometric analysis. The authors also thank Dr Zhongchi Liu （University of Maryland, USA）, Dr Chun-Ming Liu （Institute of Botany CAS, China）, Dr Terry Matthew （University of Southampton, UK）, Professor Daochun Kong （Peking University, China） and Dr Naomi Nakayama （Yale University, USA） for critical comments and valuable discussion. This work was supported by the National Natural Science Foundation of China （GN 30625002 to L-J Qu）.
文摘Water is the most abundant molecule in almost all living organisms. Aquaporins are channel proteins that play critical roles in controlling the water content of cells. Here, we report the identification of an AP2/EREBP family transcription factor in Arabidopsis thaliana, TRANSLUCENT GREEN （TG）, whose overexpression in transgenic plants gave enhanced drought tolerance and vitrified leaves. TG protein is localized in the nucleus, binds DRE and GCC elements in vitro, and acts as a transcriptional activator in yeast cells. Microarray analysis revealed a total of 330 genes regulated by TG, among which five genes encode aquaporins. A transient expression assay showed that TG directly binds to the promoters of three aquaporin genes, such as AtTIP1;1, AtTIP2;3, and AtPIP2;2, indicating that TG directly regulates the expression of these genes. Moreover, overexpression of AtTIP1;1 resulted in vitrified phenotypes in transgenic Arabidopsis plants, similar to those observed in TG overexpression lines. Water injection into wild-type leaves recapitulated the vitrified leaf phenotypes, which was reversed by cutting off the water supply from vascular bundles. Taken together, our data support that TG controls water balance in Arabidopsis through directly activating the expression of aquaporin genes.
基金supported by the National Basic Research Program of China (No. 2009CB941503)
文摘Complex I （the NADH：ubiquinone oxidoreductase） of the mitochondrial respiratory chain is a complicated, multi-subunit, membrane- bound assembly and contains more than 40 different proteins in higher plants. In this paper, we characterize the Arabidopsis homologue （designated as AtCIB22） of the B22 subunit of eukaryotic mitochondriai Complex I. AtCIB22 is a single-copy gene and is highly con- served throughout eukaryotes. AtCIB22 protein is located in mitochondria and the AtC1B22 gene is widely expressed in different tissues. Mutant Arabidopsis plants with a disrupted AtC1B22 gene display pleiotropic phenotypes including shorter roots, smaller plants and de- layed flowering. Stress analysis indicates that the AtC1B22 mutants＇ seed germination and early seedling growth are severely inhibited by sucrose deprivation stress but more tolerant to ethanol stress. Molecular analysis reveals that in moderate knockdown AtCIB22 mutants, genes including cell redox proteins and stress related proteins are significantly up-regulated, and that in severe knockdown AtCIB22 mu- tants, the alternative respiratory pathways including NDA1, NDB2, AOXla and AtPUMP1 are remarkably elevated. These data demon- strate that AtCIB22 is essential for plant development and mitochondrial electron transport chains in Arabidopsis. Our findings also en- hance our understanding about the physiological role of Complex I in plants.
基金supported by the National Natural Science Foundation of China(90717003)
文摘In plants,one of the most common modifications of secondary metabolites is methylation catalyzed by various methyltransferases. Recently,a new class of methyltransferases,the SABATH family of methyltransferases,was found to modify phytohormones and other small molecules.The SABATH methyltransferases share little sequence similarity with other well characterized methyltransferases.Arabidopsis has 24 members of the SABATH methyltransferase genes,and a subset of them has been shown to catalyze the formation of methyl esters with phytohormones and other small molecules.Physiological and genetic analyses show that methylation of phytohormones plays important roles in regulating various biological processes in plants,including stress responses,leaf development,and seed maturation/germination.In this review,we focus on phytohormone methylation by the SABATH family methyltransferases and the implication of these modifications in plant development.
文摘The Mediator complex is an important component of the eukaryotic transcriptional machinery. As an essential link between transcription factors and RNA polymerase II, the Mediator complex transduces diverse signals to genes involved in different pathways. The plant Mediator complex was recently purified and comprises conserved and specific subunits. It functions in concert with transcription factors to modulate various responses. In this review, we summarize the recent advances in understanding the plant Mediator complex and its diverse roles in plant growth, development, defense, non-coding RNA production, response to abiotic stresses, flowering, genomic stability and metabolic homeostasis. In addition, the transcription factors interacting with the Mediator complex are also highlighted.
基金supported by National Natural Science Foundation of China(31620103903)partially by the 111 projectsupported by the Peking-Tsinghua Joint Center for Life Sciences
文摘In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than double fertilization, can trigger ovule enlargement. However, it remains unclear whether the signal（s） to trigger the initiation of ovule enlargement are from the sperm cells or fromthe pollen tubes. Recently, we identified a mutant dropl- drop2-, which produces pollen tubes with no sperm cells. Taking advantage of this special genetic material, we conducted pollination assays, and found that the ovules pollinated with dropl- drop2- pollen could initiate the enlargement and exhibited significant enlarged sizes at 36h after pollination in comparison with those unpollinated ovules. However, the sizes of the ovules pollinated with drops- drop2- pollen are significantly smaller than those of the ovules pollinated with wildtype pollen. These results demonstrate that the pollen tube, rather than the sperm cells, release the signal to trigger the initiation of ovule enlargement, and that double fertilization is required for further enlargement of the seeds.
文摘The activities of transcription factors （TFs） require interactions with specific DNA sequences and other reg- ulatory proteins. To detect such interactions in Arabidopsis, we developed a high-throughput screening system with a Gateway-compatible Gal4-AD-TF library of 1589 Arabidopsis TFs, which can be easily screened by mating-based yeast-one-hybrid （YIH） and yeast-two-hybrid （Y2H） methods. The efficiency of the system was validated by examining two well-characterized TF-DNA and TF-protein interactions： the CHE-CCA1 promoter interaction by YIH and NPR1-TGAs interactions by Y2H. We used this system to identify eight TFs that interact with a Mediator subunit, Med25, a key reg- ulator in JA signaling. We identified five TFs that interacted with the GCC-box cis-element in the promoter of PDF1.2, a downstream gene of Med25. We found that three of these TFs, all from the AP2-EREBP family, interact directly both with Med25 and the GCC-box of PDF1.2, suggesting that Med25 regulates PDF1.2 expression through these three TFs. These results demonstrate that this high-throughput Y1H/Y2H screening system is an efficient tool for studying transcrip- tional regulation networks in Arabidopsis. This system will be available for other Arabidopsis researchers, and thus it provides a vital resource for the Arabidopsis community.
基金supported by the National Basic Research Program of China(No.2009CB941502)
文摘VPS 15 protein is a component of the phosphatidylinositol 3-kinase complex which plays a pivotal role in the development of yeast and mammalian cells. The knowledge about the function of its homologue in plants remains limited. Here we report that AtVPS15, a homologue of yeast VPS15p in Arabidopsis, plays an essential role in pollen germination. Homozygous T-DNA insertion mutants of AtVPS15 could not be obtained from the progenies of self-pollinated heterozygous mutants. Reciprocal crosses between atvps15 mutants and wild-type Arabidopsis revealed that the T-DNA insertion was not able to be transmitted by male gametophytes. DAPI staining, Alexander＇s stain and scanning electron microscopic analysis showed that atvps15 heterozygous plants produced pollen grains that were morphologically indistinguishable from wild-type pollen, whereas in vitro germination experiments revealed that germination of the pollen grains was defective. GUS staining analysis of transgenic plants expressing the GUS reporter gene driven by the AtVPS15 promoter showed that AtVPS15 was mainly expressed in pollen grains. Finally, DUALmembrane yeast two-hybrid analysis demonstrated that AtVPS15 might interact directly with AtVPS34. These results suggest that AtVPS15 is very important for pollen germination, possibly through modulation of the activity of PI3-kinase.
文摘In flowering plants,the two sperm cells are passive cargo transported into the ovule by pollen tubes (Zhang et al.,2017).Therefore,the precise guidance of pollen tubes is critical for successful double fertilization (Dresselhaus and Franklin-Tong,2013).A series of male-female interactions are required to guarantee the spatiotemporal regulation of pollen tube guidance because during growth,pollen tubes continuously interact with different female tissues (Zhong et al.,2017;Zhong and Qu,2019).In the past two decades,there has been tremendous progress in elucidating the molecular mechanisms of pollen tube guidance regulation,mostly using Arabidopsis thaliana as a model system (Johnson et al.,2019).
基金supported by the National Natural Science Foundation of China(Nos.31620103903 and 31621001)partially by the 111 projectsupported by the Peking-Tsinghua Joint Center for Life Sciences
文摘In plants, RNA editing is a post-transcriptional process that changes specific cytidine to uridine in both mitochondria and plastids. Most pentatricopeptide repeat（PPR） proteins are involved in organelle RNA editing by recognizing specific RNA sequences. We here report the functional characterization of a PPR protein from the DYW subclass, Baili Xi（BLX）, which contains five PPR motifs and a DYW domain. BLX is essential for early seed development, as plants lacking the BLX gene was embryo lethal and the endosperm failed to initiate cellularization. BLX was highly expressed in the embryo and endosperm, and the BLX protein was specifically localized in mitochondria, which is essential for BLX function. We found that BLX was required for the efficient editing of 36 editing sites in mitochondria. Moreover, BLX was involved in the splicing regulation of the fourth intron of nad1 and the first intron of nad2. The loss of BLX function impaired the mitochondrial function and increased the reactive oxygen species（ROS） level. Genetic complementation with truncated variants of BLX revealed that, in addition to the DYW domain, only the fifth PPR motif was essential for BLX function. The upstream sequences of the BLX-targeted editing sites are not conserved, suggesting that BLX serves as a novel and major mitochondrial editing factor（MEF） via a new non-RNA-interacting manner. This finding provides new insights into how a DYW-type PPR protein with fewer PPR motifs regulates RNA editing in plants.
基金supported by the National Key R&D Program of China(grant no.2018YFE0204700)and National Natural Science Foundation of China(grant no.31991202,31830004,31620103903,and 31621001 toLJQ,and 32070854 to Sheng Znong).The Qu laboratory is supported by the Peking-Tsinghua Joint Center for Life Sciences,and work on frti-ization and eary embryogenesis in the Dresselhaus lab is supported by the German Research Foundation DFG via Collaborative Research Center SFB960.
文摘The signaling pathway of the gaseous hormone ethylene is involved in plant reproduction,growth,devel-opment,and stress responses.During reproduction,the two synergid cells of the angiosperm female gametophyte both undergo programmed cell death(PCD)/degeneration but in a different manner:PCD/degeneration of one synergid facilitates pollen tube rupture and thereby the release of sperm cells,while PCD/degeneration of the other synergid blocks supernumerary pollen tubes.Ethylene signaling was postu-lated to participate in some of the synergid cell functions,such as pollen tube attraction and the induction of PCD/degeneration.However,ethylene-mediated induction of synergid PCD/degeneration and the role of ethylene itself have not been firmly established.Here,we employed the CRISPR/Cas9 technology to knock out the five ethylene-biosynthesis 1-aminocyclopropane-1-carboxylic acid oxidase(ACO)genes and created Arabidopsis mutants free of ethylene production.The ethylene-free mutant plants showed normal triple responses when treated with ethylene rather than 1-aminocyclopropane-1-carboxylic acid,but had increased lateral root density and enlarged petal sizes,which are typical phenotypes of mutants defective in ethylene signaling.Using these ethylene-free plants,we further demonstrated that production of ethylene is not necessarily required to trigger PCD/degeneration of the two synergid cells,but certain com-ponents of ethylene signaling including transcription factors ETHYLENE-INSENSITIVE 3(EIN3)and EIN3-LIKE 1(EIL1)are necessary for the death of the persistent synergid cell.
