Dynamics of cytosolic and organellar gene transcripts in wild and cultivated genotypes of pigeon pea due to simulated herbivory.

Pigeon pea (Cajanus cajan), widely grown in India, suffers significant yield losses due to pod borers (Helicoverpa armigera and Maruca vitrata). Therefore, studying the host resistance mechanism is pivotal for crop improvement. In this study, we conducted transcriptome analysis on two wild-type (WT) Cajanus scarabaeoides accessions (ICP-15761 and ICP-15738) having high levels of resistance to pod borers and two cultivated C. cajan genotypes, ICPL-332 (moderately resistant) and ICPL-87 (susceptible), following simulated herbivory with H. armigera oral secretions (OS). Differential gene expression analysis identified 3573 and 4677 differentially expressed genes (DEGs) in ICP-15761 and ICP-15738, whereas 4149 and 3639 DEGs were documented in ICPL-332 and ICPL-87, respectively. Genes related to chloroplast biogenesis, photosynthesis, and chlorophyll metabolism exhibited significant differential expression, indicating chloroplast reprogramming under simulated herbivory. Significant upregulation of key defense genes, including chitinases and cysteine proteases, in C. scarabaeoides accessions highlighted robust defense pathway activation. A genotype-specific shift in transcription factors, phytohormones, and calcium signaling-related gene expression was noted. Higher levels of expression of aspartic proteinases and pathogenesis-related proteins in cultivated genotypes suggesting adaptive evolutionary traits. This is a novel insight on molecular mechanism of defense in a wild type, C. scarabaeoides and cultivated genotypes of pigeon pea under simulated herbivory. The information on cytosolic and organellar gene changes in pigeon pea due to H. armigera OS mediated-simulated herbivory may help develop pigeon pea varieties that are resistant to pod borer infestations.