Comprehensive Analysis of Genes Associated with the Reactive Oxygen Species Metabolism in Citrus sinensis during Pathogen Infection

Abstract

Reactive oxygen species (ROS) are pivotal in signal transduction processes in plant–pathogen interactions. The ROS signaling pathways involved in Candidatus Liberibacter asiaticus (CLas) and Xanthomonas citri subspecies citri (Xcc) infections in Citrus sinensis (sweet orange) are unclear. In this study, we comprehensively identified ROS metabolism-associated genes, including 9 NADPH oxidase (RBOH), 14 superoxide dismutase (SOD), 1 catalase (CAT), 9 peroxiredoxin (PrxR), 5 ascorbate peroxidase (APX), 4 glutathione peroxidase (GPX), 3 monodehydroascorbate reductase (MDAR), 2 dehydroascorbate reductase (DHAR), 2 glutathione reductase (GR), 24 thioredoxin (Trx), and 18 glutaredoxin (GLR) genes in C. sinensis. An analysis revealed variable gene structures but conserved motifs and domains in ROS subfamilies. A comparative synteny analysis with Arabidopsis thaliana and Vitis vinifera indicated evolutionary conservation of most ROS metabolism-associated genes, with some originating from gene duplication events post-species divergence in C. sinensis. Expression profiling revealed five up-regulated genes and four down-regulated genes during both CLas and Xcc infections. Promoter analysis revealed numerous stress-responsive elements in the promoter of ROS metabolism-associated genes. Protein–protein interaction network analysis highlighted the involvement of ROS metabolism in various biological processes. A comparison of ROS metabolism-associated genes between C. sinensis and Poncirus trifoliata indicated multiple gene gain and loss events within ROS subfamilies of C. sinensis. This study enhances our understanding of ROS metabolism in C. sinensis and sheds light on citrus–pathogen interactions.