-Mediated Signaling Pathway in Pollen Tubes Regulates the Gametophytic Self-incompatibility of Species.

Among the Rosaceae species, the gametophytic self-incompatibility (GSI) is controlled by a single multi-allelic S locus, which is composed of the pistil-S and pollen-S genes. The pistil-S gene encodes a polymorphic ribonuclease (S-RNase), which is essential for identifying self-pollen. However, the S-RNase system has not been fully characterized. In this study, the self-S-RNase inhibited the Ca-permeable channel activity at pollen tube apices and the selectively decreased phospholipase C () activity in the plasma membrane of pollen tubes. Self-S-RNase decreased the Ca influx through a -mediated signaling pathway. Phosphatidylinositol-specific has a 26-amino acid insertion in pollen tubes of the 'Jinzhuili' cultivar, which is a spontaneous self-compatible mutant of the 'Yali' cultivar. 'Yali' plants exhibit a typical S-RNase-based GSI. Upon self-pollination, gene expression is significantly higher in 'Jinzhuili' pollen tubes than that in 'Yali' pollen tubes. Moreover, the in pollen tubes can only interact with one of the two types of S-RNase from the style. In the Rehd, the directly interacted with the S-RNase in the pollen tube, but not with the S-RNase. Collectively, our results reveal that the effects of S-RNase on activity are required for S-specific pollen rejection, and that -IP participates in the self-incompatibility reaction of species.