A Hierarchical Model of ABA-Mediated Signal Transduction in Tea Plant Revealed by Systematic Genome Mining Analysis and Interaction Validation.

As a critical signaling molecule, ABA plays an important role in plant growth, development, and stresses response. However, tea plant (Camellia sinensis), an important economical perennial woody plant, has not been systematically reported in response to ABA signal transduction in vivo. In this study, we mined and identified the gene structure of CsPYL/CsPP2C-A/CsSnRK gene families in ABA signal transduction pathway through the genome-wide analysis of tea plant. Spatiotemporal expression and stress response (drought, salt, chilling) expression patterns were characterized. The results showed that most members of CsPYLs were conserved, the gene structures of members of A type CsPP2Cs were highly similar, while the gene structure of CsSnRK2s was highly variable. The transcription levels of different family members were differentially expressed with plant growth and development, and their response to stress signal patterns was highly correlated. The expression patterns of CsPYL/CsPP2C-A/CsSnRK2 gene family members in different tissues of tea plant cuttings after exogenous ABA treatment were detected by qRT-PCR, and the hierarchical model of ABA signaling was constructed by correlation analysis to preliminarily obtain three potential ABA-dependent signaling transduction pathways. Subsequently, the protein interaction of the CsPYL4/7-CsPP2C-A2-CsSnRK2.8 signaling pathway was verified by yeast two-hybrid and surface plasmon resonance (SPR) experiments, indicating that there is specific selectivity in the ABA signaling pathway. Our results provided novel insights into ABA-dependent signal transduction model in tea plant and information for future functional characterizations of stress tolerance genes in tea plant.