摘要Pollen hydration on dry stigmas is strictly regulated by pollen-stigma interactions in Brassicaceae.Although several related molec-ular events have been described,the molecular mechanism underlying pollen hydra-tion remains elusive.Multiple B-class pollen coat proteins(PCP-Bs)are involved in pollen hydration.Here,by analyzing the interactions of two PCP-Bs with three Arabidopsis thaliana stigmas strongly expressing S-domain receptor kinase(SD-RLK),we determined that SD-RLK28 directly interacts with PCP-Bβ.We investigated pollen hydration,pollen germination,pollen tube growth,and stigma receptivity in the sd-rlk28 and pcp-bβ mutants.PCP-Bβ acts in the pollen to regulate pollen hydration on stigmas.Loss of SD-RLK28 had no effect on pollen viability,and sd-rlk28 plants had normal life cycles without obvious defects.However,pollen hydration on sd-rlk28 stigmas was im-paired and pollen tube growth in sd-rlk28 pistils was delayed.The defect in pollen hydration on sd-rlk28 stigmas was independent of changes in reactive oxygen species levels in stigmas.These results indicate that SD-RLK28 functions in the stigma as a PCP-Bβ receptor to positively regulate pollen hydration on dry stigmas.