Genome-Wide Identification of PSK Gene Family and Effects of Abscisic Acid (ABA) in Regulating Antioxidant Activity and ROS Signaling Under Drought Stress in Brassica napus

Phytosulfokine (PSK) is a tyrosine-sulfated pentapeptide found throughout the plant kingdom, playing key roles in plant growth, development, and responses to biotic and abiotic stresses. However, there is still a lack of a comprehensive analysis of the <i>BnPSK</i> gene family in <i>Brassica napus</i>. In this study, we conducted a genome-wide identification and characterized 19 <i>BnPSK</i> genes in oil seed plants, which are unevenly distributed across both sub-genomes (A and C). BnPSK proteins ranged from 77 to 99 amino acids (BnPSK3c and BnPSK3d) in length, all belonging to the PSK-α type and containing conserved PSK domains. Synteny analysis revealed that the expansion of the <i>BnPSK</i> gene family is primarily attributed to whole genome duplication, with homology to <i>Arabidopsis thaliana PSK</i> genes. A promoter region analysis identified <i>cis</i>-acting elements related to hormone and stress responses. An expression profile analysis showed that <i>BnPSK</i> genes are highly expressed in roots, leaves, petals, and pollens and are induced by both abiotic stresses and phytohormone application. Furthermore, RT-qPCR assay demonstrated that the expression levels of <i>BnPSK4c</i>, <i>BnPSK5a</i>, and <i>BnPSK5b</i> were significantly enhanced under drought stress (3~5-fold) both in plant roots and leaves following ABA application. Lastly, the application of ABA induced antioxidant activity including SOD, POD, CAT and APX (2~5-fold) and their corresponding genes (3~5-fold), and altered the ROS-signaling in rapeseed plants; also, strong evidence of mitigating drought stress was present. These findings establish a basis for further research into the role of the <i>BnPSK</i> gene family in oilseed plant tolerance against drought stress and underlying molecular mechanisms, offering valuable perspectives for developing novel peptides.