Dear Editor,In most flowering plants, the stigma of the flower represents the barrier that prevents any unrelated or incompatible （genetically similar） pollen from germination and fertilizing the ovule, leading to e...Dear Editor,In most flowering plants, the stigma of the flower represents the barrier that prevents any unrelated or incompatible （genetically similar） pollen from germination and fertilizing the ovule, leading to either defective or genetically unfavorable embryos. In Brassicaceae, self-incompatibility （SI） is a genetic mechanism in the stigmas that can discern compatible versus incompatible mate （pollen）, in turn, rejecting self or incompatible pollen, while allowing non-self or compatible pollen to develop successfully to fertilize the ovules. Thus, stigmas have evolved complex mechanisms and specialized proteins to reject incompatible mates and to recognize and accept compatible pollen （Doucet et al., 2016）. The fact that SI has been shown to exclusively operate in the stigmas temporally before and during anthesis （Kandasamy et al., 1993） indicates that multiple metabolic pathways essential for pollination exist in these stigmatic papillary cells.展开更多
In angiosperms,the process of pollination relies on species-specific interaction and signaling between the male(pollen)and female(pistil)counterparts where the interplay between several pollen and stigma proteins deci...In angiosperms,the process of pollination relies on species-specific interaction and signaling between the male(pollen)and female(pistil)counterparts where the interplay between several pollen and stigma proteins decides the fate of the pollen.In Brassicaceae,the dry stigmatic papillary cells control pollen germination by releasing resources only to compatible pollen thereby allowing pollen to hydrate and germinate.Despite the identification of a number of stigmatic proteins that facilitate pollination responses,the signaling mechanisms that regulate functions of these proteins have remained unknown.Here,we show that,in Arabidopsis,an extremely functionally redundant mitogen-activated protein kinase(MAPK)cascade is required for maintaining stigma receptivity to accept compatible pollen.Our genetic analyses demonstrate that in stigmas,five MAPK kinases(MKKs),MKK1/2/3/7/9 are required to transmit upstream signals to two MPKs,MPK3/4,to mediate compatible pollination.Compromised functions of these five MKKs in the quintuple mutant(mkk1/2/3RNAi/mkk7/9)phenocopied pollination defects observed in the m pk4RNAi/m pk3 double mutant.We further show that this MAPK nexus converges on Exo70A1,a previously identified stigma receptivity factor essential for pollination.Given that pollination is the crucial initial step during plant reproduction,understanding the mechanisms that govern successful pollination could lead to development of strategies to improve crop yield.展开更多
Dear Editor,Many flowering plants utilize the self-incompatibility(SI)response as a genetic mechanism to prevent self-pollen from establishing on the stigmas,thereby promoting outcrossing and genetic diversity.In Bras...Dear Editor,Many flowering plants utilize the self-incompatibility(SI)response as a genetic mechanism to prevent self-pollen from establishing on the stigmas,thereby promoting outcrossing and genetic diversity.In Brassica during SI,recognition of the pollen ligand SP11 by S-locus receptor kinase(SRK)results in activation of the E3 ligase ARM-Repeat-Containing protein(ARC1),which leads to proteasomal degradation of compatibility factors required for successful pollen acceptance.展开更多
文摘Dear Editor,In most flowering plants, the stigma of the flower represents the barrier that prevents any unrelated or incompatible （genetically similar） pollen from germination and fertilizing the ovule, leading to either defective or genetically unfavorable embryos. In Brassicaceae, self-incompatibility （SI） is a genetic mechanism in the stigmas that can discern compatible versus incompatible mate （pollen）, in turn, rejecting self or incompatible pollen, while allowing non-self or compatible pollen to develop successfully to fertilize the ovules. Thus, stigmas have evolved complex mechanisms and specialized proteins to reject incompatible mates and to recognize and accept compatible pollen （Doucet et al., 2016）. The fact that SI has been shown to exclusively operate in the stigmas temporally before and during anthesis （Kandasamy et al., 1993） indicates that multiple metabolic pathways essential for pollination exist in these stigmatic papillary cells.
基金Natural Sciences and Engineering Research Council of Canada funding for M.A.S.
文摘In angiosperms,the process of pollination relies on species-specific interaction and signaling between the male(pollen)and female(pistil)counterparts where the interplay between several pollen and stigma proteins decides the fate of the pollen.In Brassicaceae,the dry stigmatic papillary cells control pollen germination by releasing resources only to compatible pollen thereby allowing pollen to hydrate and germinate.Despite the identification of a number of stigmatic proteins that facilitate pollination responses,the signaling mechanisms that regulate functions of these proteins have remained unknown.Here,we show that,in Arabidopsis,an extremely functionally redundant mitogen-activated protein kinase(MAPK)cascade is required for maintaining stigma receptivity to accept compatible pollen.Our genetic analyses demonstrate that in stigmas,five MAPK kinases(MKKs),MKK1/2/3/7/9 are required to transmit upstream signals to two MPKs,MPK3/4,to mediate compatible pollination.Compromised functions of these five MKKs in the quintuple mutant(mkk1/2/3RNAi/mkk7/9)phenocopied pollination defects observed in the m pk4RNAi/m pk3 double mutant.We further show that this MAPK nexus converges on Exo70A1,a previously identified stigma receptivity factor essential for pollination.Given that pollination is the crucial initial step during plant reproduction,understanding the mechanisms that govern successful pollination could lead to development of strategies to improve crop yield.
基金supported by the Natural Sciences and Engineering Research Council of Canada for M.A.S.,K.A.,and N.M.N.H.X.L.was supported by the National Natural Science Foundation of China(31870300)Heilongjiang Touyan Innovation Team Program(Tree Genetics and Breeding Innovation Team).
文摘Dear Editor,Many flowering plants utilize the self-incompatibility(SI)response as a genetic mechanism to prevent self-pollen from establishing on the stigmas,thereby promoting outcrossing and genetic diversity.In Brassica during SI,recognition of the pollen ligand SP11 by S-locus receptor kinase(SRK)results in activation of the E3 ligase ARM-Repeat-Containing protein(ARC1),which leads to proteasomal degradation of compatibility factors required for successful pollen acceptance.
