Genome-wide identification of castor bean OSCA genes and analysis of expression patterns under drought and salt stress

OSCA (hyperosmolality-gated calcium-permeable channel) is an important class of mechanosensitive calcium channels in plants. OSCAs, which was located on the plasma membrane, function as osmosensors that enable plants to perceive hyperosmotic environments, such as drought and salt stress, and initiate downstream calcium ions signaling. However, a systematic genome-wide identification and functional characterization of the OSCA gene family in castor bean (Ricinus communis L. ) under abiotic stresses remain unelucidated. In this study, we conducted a comprehensive genome-wide identification and analysis of the OSCA gene family in castor bean using bioinformatics approaches based on its whole-genome sequence. A total of 10 OSCA genes (RcOSCAs) were identified, which were unevenly distributed on five chromosomes. Phylogenetic analysis classified the RcOSCA proteins into four distinct subfamilies and clarified their evolutionary relationships with homologs from Arabidopsis thaliana, Oryza sativa, Triticum aestivum, Zea mays, and Glycine max. All proteins encoded by RcOSCA genes contain three conserved domains including RSN1TM, PHM7cyt, and RSN1₇TM. RT-qPCR analysis displayed that the transcript levels of several RcOSCA genes were significantly upregulated in roots, true leaves, or cotyledons under drought or salt stress. Notably, RcOSCA6 was rapidly and strongly induced in true leaves within 6 h of salt stress, highlighting its potential key role in castor bean's adaptation to abiotic stress. This study constitutes the first genome-wide identification of the OSCA gene family in castor bean and provides preliminary insights into its evolutionary features and, more importantly, the species- and tissue-specific expression dynamics under salt and drought stresses. Future functional studies are warranted to fully elucidate the roles of these RcOSCAs in stress adaptation. These results contribute to understanding the molecular mechanisms underlying drought and salt tolerance in this resilient oil crop and offer valuable candidate genes for future functional characterization.