Genome-Wide Identification and Analysis of Plant Cysteine Oxidase (PCO) Gene Family in Brassicaceae and Their Roles in Abiotic Stress Response

Plant Cysteine Oxidase (PCO) is a plant O2-sensing enzyme of catalyzing oxidation of cysteine to Cys-sulfinic acid at the N-termini of target proteins. To better understand the Brassica napus PCO gene family, PCO genes in B. napus and related species were analyzed. In this study, 20, 7 and 8 PCO genes were identified in Brassica napus, Brassica rapa and Brassica oleracea, respectively. According to phylogenetic analysis, the PCOs were divided into five groups: PCO1, PCO2, PCO3, PCO4 and PCO5. Gene organization and motif distribution analysis suggested that PCO gene family was relatively conserved during evolution. Expression analysis showed that PCO genes were expressed in different tissues at different developmental stages. Interestingly, most of the Bna/Br/BoPCO5 members were expressed in leaves, roots, flowers, buds and siliques, suggesting an important role in both vegetative and reproductive development. Expression of BnaPCO was induced by various abiotic stress, especially waterlogging stress, which was consistent with the result of cis-element analysis. In this study, the PCO gene family of Brassicaceae was analyzed for the first time, which contributes to a comprehensive understanding of the origin and evolution of PCO genes in Brassicaceae and the function of BnaPCO in regulating plant responses to abiotic stresses.