Genome-Wide Identification and Functional Analysis of Chitinase Gene Family in Grape

Abstract Background: Chitinases, the important resistance-related proteins, are crucial hydrolytic enzymes, which attack fungal pathogens by catalyzing the fungal cell wall degradation. As a large gene family, the VvChis have not been systematically analyzed and effectively investigated in grape. Results: In this study, we identified 42 VvChis in grape by searching the conserved domains, and divided them into A, B, C, D and E groups according to pylogenetic relationships, gene structure and conserved domains analysis. Quantitative real-time PCR (qRT-PCR) and publicly microarray data analysis revealed distinct temporal and spatial expression patterns of VvChis in different tissues at various growth stages. The transcriptional level of most genes was high in the root of ‘Koyho’ and ‘Summer Black’. Combining cis-elements in the promoter, GO and KEGG analysis, and prediction of interaction proteins, we revealed the function of Chitinase. After the pathogen infecting the leaves and berries of grape, the expression levels of VvChis in A, B and E groups showed a significant upward trend, of which VvChi5, VvChi25, VvChi11 (leaf) and VvChi16 (fruit) were the most up-regulated. The interaction between Chi-17 and Metallothionein (MTL) was confirmed by yeast two-hybrid system and bimolecular fluorescence complementation (BiFC). In addition, VvChis in GH18 family were up-regulated under MeJA and ETH treatment, in particular to 500 mg·L -1 ETH、50 μmol·L -1 MeJA; The induction of VvChis by low temperature was more significant than that of high temperature; The expression of VvChis was positively correlated with the concentration of NaCl treatment. Conclusion: This study clarified the member composition and expression pattern of VvChi family in grape, initially explored the disease resistance function of VvChi, and analyzed the response of VvChis to hormones (MeJA and ETH) and environmental stress (temperature and NaCl) signals was analyzed, which laid a foundation for constructing the functional regulation network of VvChi in grapes.