Pan-genome cloning and expression analysis of S-RNase homologous gene in SI and SC of different tomato species

Flowering plants encode polymorphic ribonucleases (S-RNases) that determine the self-incompatibility (SI) phenotype of the style. The pan-genome cloning and expression analysis of the S-RNase homologous genes in SI and self-compatibility (SC) lines of different tomato species have not been reported. In this study, partial sequences of cDNA and DNA of the S-RNase homologous gene (designated ZS) were obtained from S. pimpinellifolium, S. Lycopersicum, S. habrochaites and S. chilense which included SI lines and SC lines. Tissue-specific expression of the S-RNase gene was detected using semi-quantitative RT-PCR and quantitative real-time PCR. We selected 6 ZS genes (two come from the SI lines and four come from SC lines) which come from different tomato species mentioned in this paper to research. ZS genes were exclusively in styles and there were significant differences in expression level of the different tomato species. The expression level of the ZS genes in the styles of the SI tomato clade S. chilense was higher than that in the SC tomato clades S. pimpinellifolium and S. lycopersicum. And, the SC tomato clade S. habrochaites, in which the expression level of the ZS genes was even higher than that in the SI tomato clade S. chilense. The outcomes presented in this research provide the basis for future deeper investigation of the molecular mechanism of SI in tomato.