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, Self-incompatibility （SI） is a genetic mechanism through which flowering plants prevent self-pollination to ensure out- crossing and genetic diversity. In Brassica sp., this mechanism is controlled by ...Dear Editor, Self-incompatibility （SI） is a genetic mechanism through which flowering plants prevent self-pollination to ensure out- crossing and genetic diversity. In Brassica sp., this mechanism is controlled by the self-incompatibility （S） locus, in which, the stigmatic ＇S-locus receptor kinase （SRK）＇ recognizes the ＇S-locus cysteine rich protein （SCR）＇ from the self-pollen to elicit an active rejection response. This results in blocking of compatibil- ity factors from being delivered to the site of pollen attachment leading to self-pollen rejection （Chapman and Goring, 2010）. In contrast, following recognition of compatible signals from the cross-pollen or compatible pollen （CP）, the stigma releases its resources such as water and nutrients to the dry pollen so that the pollen tube can germinate and penetrate the stigmatic cuticle leading to successful fertilization. Thus, an incompatible or self-pollen is fully capable of eliciting a compatible response, but is actively rejected before compatible responses can occur.展开更多
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.
文摘Dear Editor, Self-incompatibility （SI） is a genetic mechanism through which flowering plants prevent self-pollination to ensure out- crossing and genetic diversity. In Brassica sp., this mechanism is controlled by the self-incompatibility （S） locus, in which, the stigmatic ＇S-locus receptor kinase （SRK）＇ recognizes the ＇S-locus cysteine rich protein （SCR）＇ from the self-pollen to elicit an active rejection response. This results in blocking of compatibil- ity factors from being delivered to the site of pollen attachment leading to self-pollen rejection （Chapman and Goring, 2010）. In contrast, following recognition of compatible signals from the cross-pollen or compatible pollen （CP）, the stigma releases its resources such as water and nutrients to the dry pollen so that the pollen tube can germinate and penetrate the stigmatic cuticle leading to successful fertilization. Thus, an incompatible or self-pollen is fully capable of eliciting a compatible response, but is actively rejected before compatible responses can occur.
