Genes Participate in the Ubiquitination and Degradation Reaction of S-RNase in Self-compatible Peach.

It has been proved that the gametophytic self-incompatibility (GSI), mainly exists in Rosaceae and Solanaceae, is controlled by genes, which are two tightly linked genes located at highly polymorphic -locus: the for pistil specificity and the F-box gene () for pollen specificity, respectively. However, the roles of those genes in SI of peach are still a subject of extensive debate. In our study, we selected 37 representative varieties according to the evolution route of peach and identified their genotypes. We cloned pollen determinant genes mutated , and normal , and style determinant genes , and . The mutated encode truncated SFB proteins due to a fragment insertion. The truncated PperSFBs and normal PperSFB2 interacted with PperS-RNases demonstrated by Y2H. Normal was divided into four parts: box, box-V1, V1-V2, and HVa-HVb. The box domain of PperSFB2 did not interact with PperS-RNases, both of the box-V1 and V1-V2 had interactions with PperS-RNases, while the hypervariable region of HVa-HVb only interacted with PperS2-RNase showed by Y2H and BiFC assay. Bioinformatics analysis of peach genome revealed that there were other F-box genes located at S-locus, and of which three F-box genes were specifically expressed in pollen, named as , and , respectively. In phylogenetic analysis clustered with Maloideae genes, and genes were clustered into the other group with other genes of . Protein interaction analysis revealed that the three PperSLFLs interacted with PperSSK1 and PperS-RNases with no allelic specificity. ubiquitination assay showed that PperSLFLs could tag ubiquitin molecules onto PperS-RNases. The above results suggest that three PperSLFLs are the appropriate candidates for the "general inhibitor," which would inactivate the S-RNases in pollen tubes, involved in the self-incompatibility of peach.