Characterization of invertase inhibitors (InvInhs) in tea plant, and their potential roles in participating in growth, development and cold response

Invertase inhibitor (InvInh) represses acid invertase (AI) activity though interacting with AI at post-translation level, which plays important roles in vegetative and reproductive processes and stress responses of plant. Our previous studies revealed that CsAI genes were involved in regulating cold response of tea plant, while the post-translation regulation mechanism of AI and the roles of InvInh in tea plant have not been reported yet. Herein, we identified 4 CsInvInhs, including 2 tandem repeat genes (CsInvInh1/2) and 2 segmental duplication genes (CsInvInh3/4), from three sequenced tea plant genomes, and further purified CsInvInh1/2 proteins. Bioinformatics analysis results showed that both of CsInvInh1/2 were located on chromosome (Chr) 5, while CsInvInh3/4 were respectively located on Chr9 and Chr12, which was consistent with the results of inter-species collinearity analysis. Under various abiotic stress conditions, the transcription levels of CsInvInhs were induced with different extent at different treatment time points. In addition, all of CsInvInhs differentially expressed among different tea plant cultivars under drought stress condition. Moreover, CsInvInh1/2 shared similar expression patterns in different tea plant tissues, and under cold stress or cold acclimation conditions, suggesting that CsInvInh1/2 may have functional redundancy in tea plant. Correlation analysis results showed that the changes of CWIN and VIN activities were not significantly correlated with the expression patterns of 5 CsAI genes, while negatively correlated with the expression patterns of 3 CsInvInhs in different tea plant tissues, and under cold stress or cold acclimation conditions, indicating that CsInvInhs participate in growth, development and cold response of tea plant mainly through inhibiting AI activity. These results will provide theoretical foundation for the cold-resistant molecular mechanism of tea plant, and also provide new genetic resources and approaches for cold-resistant molecular breeding of tea plant.