Quantitative analysis of pathogenesis-related protein expression in Gossypium hirsutum L. to elicitor-induced resistance against cotton leaf curl disease and predicted in-silico protein-protein interactions

Systemic acquired resistance (SAR) can offer an effective management strategy for plant diseases. Pathogenesis-related (PR) gene expression was investigated in Gossypium hirsutum plants in response to SAR induced by the exogenous application of salicylic acid, jasmonic acid, and benzothiadiazole as elicitors, followed by inoculation with Cotton leaf curl Multan virus (CLCuMuV). Expression of cotton, PR genes encoded on multiple loci were determined by qPCR. Primers were designed based on sequence regions conserved in each group of aligned gene targets in the annotated Gossypium hirsutum reference genome assembly. While designing primers for gene expression analysis, the copy number variation (CNV) was mitigated using bioinformatics and alignment tools to craft primers specific to their target genes. Gene expression of pathogenesis-related proteins such as PR1, PR4, PR5, β 1,3 glucanase, and chitinase was quantified by qPCR. In silico protein interactions were predicted between the five PR and begomoviral proteins using Phyre 2. The results indicated that all the PR genes were expressed on the 2^nd date of analysis. The exogenous benzothiadiazole (BTH) application significantly increased all PR gene expression and suppressed the virus infection. The application of BTH after virus inoculation significantly enhanced systemic acquired resistance, which indicates that virus infection initially triggered SAR, and subsequent application of elicitor, i.e., BTH, further facilitated the signal transduction for the expression of PR genes. In silico interactions predicted significant interactions between CLCuMuV coat protein (AV1) gene and Chitinase, PR1, PR5, whereas the replication-associated gene, AC1, interacted with PR1. Results indicate that cotton PR genes suppress the CLCuMuV infection in G. hirsutum plants. The identified PR genes could be exploited to enhance resistance through genetic transformation in cotton plants to control CLCuMuV.