Kinome profiling of Jatropha curcas L. reveals early responses to salinity stress

Introduction: Jatropha curcas L. is an important oilseed species with potential for cultivation in marginal environments; however, the molecular mechanisms underlying its responses to abiotic stress remain incompletely understood. Protein kinases (PKs) play central roles in stress perception and signal transduction, yet their involvement in salinity responses in J. curcas remains poorly characterized. Materials and methods: The J. curcas kinome was characterized using the reference genome and classified into kinase groups and families. Transcriptomic datasets previously generated from two contrasting accessions exposed to 150 mM NaCl for 3 h were reanalyzed to investigate the expression of PK genes under early salinity stress. Structural, regulatory, functional enrichment, and transcription factor (TF) association analyses were performed, and selected candidates were validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Results: A total of 1350 PK transcripts encoded by 872 unique genes were identified, representing approximately 2.9% of the predicted protein-coding genes in the genome. These genes were classified into 20 kinase groups and 121 families/subfamilies, with receptor-like kinase/Pelle (RLK-Pelle) representing the largest and most diverse group. Promoter analyses identified diverse putative cis-regulatory elements associated with multiple TF families. Transcriptomic analyses revealed marked differences between accessions. The less salt-tolerant accession Jc171 exhibited extensive transcriptional reprogramming, with 257 differentially expressed kinase genes, whereas the salt tolerant-like accession Jc183 displayed only 20 differentially expressed kinase genes. Functional enrichment analyses indicated activation of stress-responsive pathways and repression of growth-related processes in Jc171, whereas Jc183 exhibited comparatively limited functional enrichment. RT-qPCR analyses generally supported the expression trends observed for selected kinase candidates. Conclusions: This study expands current knowledge of kinase-mediated signaling in J. curcas and identifies salinity-responsive genes, regulatory signatures, and putative signaling networks associated with early salt stress responses. The results provide a valuable resource for future functional studies and crop improvement strategies aimed at enhancing abiotic stress resilience.