Genome-wide identification of CDPK genes in Ricinus communis L. and functional characterization of RcCDPK18 in osmotic stress response

Castor is an important industrial oilseed crop, and castor oil extracted from its seeds is an important industrial raw material. However, drought severely restricts castor yield. Although CDPKs function as key regulators of plant growth, development, and stress adaptation, the RcCDPK gene family has not yet been characterized in castor. In this study, we identified and analyzed the drought resistance capabilities of the RcCDPK gene family. In this study, we identified the RcCDPK genes and assessed their roles in drought resistance. Eighteen RcCDPK genes were identified and classified into five subfamilies. Chromosomal localization revealed that members of this gene family were distributed across nine chromosomes. Gene structure, conserved motifs, and multiple sequence alignment analyses demonstrated that the RcCDPK gene family was highly conserved. Analysis of promoter cis-acting elements showed that this family contains ABA- and MeJA-responsive elements. In addition, protein-protein interaction analysis revealed that RcCDPK family members interact with the respiratory oxidase proteins RBOHB, RBOHE, and RBOHF. qRT-PCR analysis showed that RcCDPK18 was upregulated in the roots and leaves of castor plants under drought stress. RcCDPK18 was overexpressed in Arabidopsis and castor through genetic transformation. Phenotypic, physiological, and biochemical analyses under drought stress showed that RcCDPK18-overexpressing Arabidopsis and castor plants exhibited stronger drought tolerance and antioxidant capacity than wild-type plants. These findings provide a theoretical basis for understanding the role of the RcCDPK gene family in drought resistance in castor and lay the groundwork for further research into the mechanisms underlying drought resistance.