Genome-wide characterization of ascorbate peroxidase gene family in pepper ( Capsicum annuum L.) in response to multiple abiotic stresses.

Pepper is widely grown all over the world, so it faces many abiotic stresses, such as drought, high temperature, low temperature, salt damage, and so on. Stresses causing the accumulation of reactive oxidative species (ROS) in plants are removed by antioxidant defense systems, and ascorbate peroxidase (APX) is an important antioxidant enzyme. Therefore, the present study performed genome-wide identification of the gene family in pepper. We identified nine members of the gene family in the pepper genome according to the APX proteins' conserved domain in . The physicochemical property analysis showed that had the longest protein sequence and the largest molecular weight of all genes, while had the shortest protein sequence and the smallest MW. The gene structure analysis showed that were composed of seven to 10 introns. The genes were divided into four groups. The genes of groups I and IV were localized in the peroxisomes and chloroplasts, respectively; the group II genes were localized in the chloroplasts and mitochondria; and the group III genes were located in the cytoplasm and extracell. The conservative motif analysis showed that all genes in the pepper had motif 2, motif 3, and motif 5. The gene family members were distributed on five chromosomes (Chr. 2, 4, 6, 8, and 9). The -acting element analysis showed that most genes contain a variety of -elements related to plant hormones and abiotic stress. RNA-seq expression analysis showed that the expression patterns of nine were different in vegetative and reproductive organs at different growth and development stages. In addition, the qRT-PCR analysis of the genes revealed significant differential expression in response to high temperature, low temperature, and salinity stresses in leaf tissue. In conclusion, our study identified the gene family members in the pepper and predicted the functions of this gene family, which would provide resources for further functional characterization of genes.