Molecular characterization of REM genes in Cajanus cajan suggests the role of CcREM1 and CcREM6 like genes in heat stress response

The increasing temperature is a major threat to plant growth and development. It severely alters various biochemical and physiological processes and ultimately affects the overall crop yield. The membrane-based remorin protein-encoding genes (REM) were previously reported as significantly involved in the regulation of various biotic and abiotic stressors. However, these REM genes were not studied in Cajanus Cajan, the sixth most important legume crop due to its rich protein source and traditional medicinal plant. In this study, 17 REM gene orthologs were identified in C. cajan against A. thaliana REM genes and verified through the presence of conserved REM-related domains. Phylogenetic analysis revealed that REM genes were divided into six different groups. All the REM genes were unevenly distributed on 11 chromosomes of C. cajan. 3D protein structures and intron-exon organization indicate conserved evolutionary pattern within C. cajan. Various core, hormone-responsive, and stress-responsive cis-regulatory elements were found in promoter regions of REM genes, including TATA-box, CAAT-box, MYB, and G-box. The total estimation of antioxidant enzyme activity revealed the increase in POD and SOD activity, potentially due to a defense mechanism in response to high temperature. RNA sequencing data processing reveals higher expression of CcREM genes in leaf and flower, including CcREM1.1 and CcREM1.2. Furthermore, the differential change in expression was observed in response to high-temperature stress. Among these genes, one upregulated gene (CcREM1.3) and two downregulated genes (CcREM6.1 and CcREM6.5) are potential candidate targets for heat stress response, followed by qRT-PCR validation. Our findings suggest that CcREM1-like and CcREM6-like genes hold significant potential for future climate-smart heat-tolerant breeding of C. cajan.