Genome-wide characterization and expression patterns of chitinase genes in the pigeonpea (Cajanus cajan (L.) Millsp.) genome

Plant chitinases are involved in defense as well as a wide range of physiological functions in plants, including germination, embryogenesis, flowering, and senescence. This study was conducted to identify and annotate the chitinase-related genes from the pigeonpea genome version 2.0, their chromosomal localization and phylogenetic relationship with chitinase genes from 13 different plant species. Here, we report the identification of 34 putative chitinase genes in the pigeonpea genome. These 34 genes encode proteins belonging to two functional domain families, and are subdivided into four classes matching four of the five chitinase classes in Arabidopsis. These chitinase genes are present in clusters on the chromosome. We investigated the expression patterns of these chitinases in 29 different tissues at five developmental stages. There was clear clustering of the chitinase genes into three groups based on their expression patterns in tissues. We identified two chitinase genes C_caj-24 and C_caj-25 that were highly expressed in all tissues as well as other chitinase genes with tissue-specific expression, which suggests that they play important roles in plant defense at specific developmental stages. This information on pigeonpea chitinases could be useful for the development of pigeonpea varieties that are resistant to insect pests and fungal diseases.