Interaction Between AtCML9 and AtMLO10 Regulates Pollen Tube Development and Seed Setting.

In higher-plant reproduction, the compatibility of pollen tube germination in the pistil is essential for successful double fertilization. It has been reported thatMildew Locus O(MLO) family geneNTA(MLO7), expressing in synergid cells, can correctly guide pollen tubes. However, the molecular mechanism underlying the interacting partners to MLOs in the fertilization is still unknown. In our study, we identified the direct protein interaction between CML9 and MLO10 within a non-canonical CaMBD. In GUS reporter assays,CML9expresses in a high level in pollens, whereasMLO10can be specifically detected in stigma which reaches up to a peaking level before fertilization. Therefore, the spatio-temporal expression patterns ofMLO10andCML9are required for the time-window of pollination. When we observed the pollen germinationin vitro, twocml9mutant alleles dramatically reduced germination rate by 15% compared to wild-type. Consistently, the elongation rate of pollen tubesin plantawas obviously slow while manually pollinatingcml9-1pollens tomlo10-1stigmas. Additionally,cml9-1 mlo10-1double mutant alleles had relatively lower rate of seed setting. Taken together, protein interaction between MLO10 and CML9 is supposed to affect pollen tube elongation and further affect seed development.