Cloning and characterization of an S-RNase gene in Camellia sinensis

- A putative CsS-RNase gene (KU852488) was cloned and characterized in Camellia sinensis.
- The CsS-RNase is primarily expressed in the styles.
- The expression of CsS-RNase in self-pollinated styles was up-regulated earlier than the crossed treatments.
- The amino acid sequences of CsS-RNase were polymorphic in different tea cultivars.
- The CsS-RNase was mapped on a genetic linkage map of C. sinensis.

Self-incompatibility (SI) prevents inbreeding depression in angiosperms. Camellia sinensis is an important cash crop, but breeding improvements and genetic studies of the plant are hindered by SI. However, the SI mechanism in C. sinensis remains unclear. In this study, a putative S-RNase gene (KU852488) was cloned from C. sinensis. The full-length cDNA of CsS-RNase is 1121 bp, which encodes 238 amino acids. It shares the closest relationship with an S-RNase gene (ADA67883.1), which was cloned from a self-incompatibility Citrus reticulata cultivar 'Wuzishatangju'. The expression level of CsS-RNase in the styles were 3-259 ('Fuding Dabaicha') and 5.6-119 ('Zhongcha108') times higher than the other tissues, for example petals, pollen grains, filaments and buds. And its expression rose in self-pollinated styles with 24 h earlier than cross-pollinated styles. The genotypes of CsS-RNase in 10 cultivars and one breeding line of C. sinensis were analyzed. Totally, 11 polymorphic amino acid residues were identified. A single nucleotide polymorphism (SNP) marker of CsS-RNase was developed. Finally, the CsS-RNase was mapped onto a reference genetic linkage map of tea plant.