Integration of gene expression analysis and molecular docking in revealing stress-responsive functions of potato chitinases.

Chitin, a long-chain polymer of N-acetylglucosamine units, is a major structural component of the cell walls of many fungi and oomycetes and serves as a strong potent elicitor of plant immune responses. Chitinases are hydrolytic enzymes that degrade chitin, and play important roles in plant defence against pathogens as well as in response to various abiotic stresses. In this study, RNA-seq data were analysed to identify chitinase genes with the high expression levels under drought and disease stress conditions. Candidate genes were further investigated using homology modelling, molecular docking, and experimental validation through qRT-PCR analysis. Among the candidate genes analysed, Class I chitinase exhibited the highest expression under both stress conditions. Class III chitinase showed no significant response to chitin treatment but was significantly upregulated under drought stress. Class IV chitinase was induced under both treatments, with a stronger response to chitin application than to drought stress. In contrast, Class V chitinase was downregulated under drought stress but markedly upregulated following chitin treatment. Molecular docking analysis indicated strong binding of chitin ligands to key catalytic residues of Class V chitinase, supporting its direct role in chitin degradation and suggesting its involvement in the activation of pattern-triggered immunity (PTI) in response to pathogen attack.