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
Successful double fertilization and subsequent seed development in flowering plants requires the delivery of two sperm cells, transported by a pollen tube, into the embryo sac of an ovule. The embryo sac cells tightly...Successful double fertilization and subsequent seed development in flowering plants requires the delivery of two sperm cells, transported by a pollen tube, into the embryo sac of an ovule. The embryo sac cells tightly control synergid cell death, and as a result the polyspermy block. Arabinogalactan proteins are highly glycosylated proteins thought to be involved in several steps of the reproductive process. We show that JAGGER, Arabinogalactan Protein 4, is an important molecule necessary to prevent the growth of multiple pollen tubes into one embryo sac in Arabidopsis thaliana. In jagger, an AGP4 knockout mutant, the pistils show impaired pollen tube blockage as a consequence of the survival of the persistent synergid. JAGGER seems to be involved in the signaling pathway that leads to a blockage of pollen tube attraction. Our results shed light on the mechanism responsible for preventing polyspermy in Arabidopsis and for safe- guarding successful fertilization of all ovules in one pistil, ensuring seed set and the next generation.展开更多
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.
文摘Successful double fertilization and subsequent seed development in flowering plants requires the delivery of two sperm cells, transported by a pollen tube, into the embryo sac of an ovule. The embryo sac cells tightly control synergid cell death, and as a result the polyspermy block. Arabinogalactan proteins are highly glycosylated proteins thought to be involved in several steps of the reproductive process. We show that JAGGER, Arabinogalactan Protein 4, is an important molecule necessary to prevent the growth of multiple pollen tubes into one embryo sac in Arabidopsis thaliana. In jagger, an AGP4 knockout mutant, the pistils show impaired pollen tube blockage as a consequence of the survival of the persistent synergid. JAGGER seems to be involved in the signaling pathway that leads to a blockage of pollen tube attraction. Our results shed light on the mechanism responsible for preventing polyspermy in Arabidopsis and for safe- guarding successful fertilization of all ovules in one pistil, ensuring seed set and the next generation.
