PPR proteins in the tea plant (Camellia sinensis) and their potential roles in the leaf color changes

Pentatricopeptide repeat (PPR) family protein is one of the largest protein families in plants, which is involved in many biological processes, including transcription, RNA stabilization, RNA cleavage, RNA splicing, RNA editing, and translation of organelle genes, thereby affecting the expression of the organelle genes. However, the corresponding PPR protein in tea plants has not been investigated. In this study, 578 CsPPR genes were identified in tea plants (Camellia sinensis); the PPR motifs, types of PPR proteins, subcellular locations, gene structure, conserved motifs, phylogenetic relationships, and GO annotation were analyzed. Based on motif structure and evolutionary relationship, these genes were divided into the P subfamily and PLS subfamily. GO annotation indicated that most PPR proteins had binding activity, including RNA and DNA binding. Transcriptome and expression profile analyses suggested that 22 CsPPR genes might be related to the etiolation and albino process of tea plants. SNP analysis found that 28 SNP loci were related to the albino of HB1, and 16 SNP loci were related to the etiolation of HJYa. 12 CsPPR proteins that may be combined with chloroplast genes were found to use the PPR codes. According to the expression profile and SNP analysis, CsPPR178, CsPPR332, and CsPPR368 might have a close relationship with the albino and etiolation of tea leaves. This study provides comprehensive insights into the CsPPR proteins, which may contribute to further study of the role of CsPPR proteins on the albino and etiolation of tea leaves.