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zhangjh069975

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[交流] Disruption of the pollen-expressed FERONIA homologs

The precise delivery of male to female gametes during reproduction in eukaryotes requires complex signal exchanges and a flawless
communication between male and female tissues. In angiosperms, molecular mechanisms have recently been revealed that are
crucial for the dialog between male (pollen tube) and female gametophytes required for successful sperm delivery. When pollen
tubes reach the female gametophyte, they arrest growth, burst and discharge their sperm cells. These processes are under the
control of the female gametophyte via the receptor-like serine-threonine kinase (RLK) FERONIA (FER). However, the male signaling
components that control the sperm delivery remain elusive. Here, we show that ANXUR1 and ANXUR2 (ANX1, ANX2), which
encode the closest homologs of the FER-RLK in Arabidopsis, are preferentially expressed in pollen. Moreover, ANX1-YFP and ANX2-
YFP fusion proteins display polar localization to the plasma membrane at the tip of the pollen tube. Finally, genetic analyses
demonstrate that ANX1 and ANX2 function redundantly to control the timing of pollen tube discharge as anx1 anx2 doublemutant
pollen tubes cease their growth and burst in vitro and fail to reach the female gametophytes in vivo. We propose that ANXRLKs
constitutively inhibit pollen tube rupture and sperm discharge at the tip of growing pollen tubes to sustain their growth
within maternal tissues until they reach the female gametophytes. Upon arrival, the female FER-dependent signaling cascade is
activated to mediate pollen tube reception and fertilization, while male ANX-dependent signaling is deactivated, enabling the
pollen tube to rupture and deliver its sperm cells to effect fertilization.
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