The Glutathione Peroxidase Gene Family in Nitraria sibirica : Genome-Wide Identification, Classification, and Gene Expression Analysis under Stress Conditions.

Plant glutathione peroxidases (GPXs) are the main enzymes in the antioxidant defense system that sustain H 2 O 2 homeostasis and normalize plant reaction to abiotic stress conditions. However, the genome-wide identification of the GPX gene family and its responses to environmental stresses, especially salt stress, in Nitraria sibirica , which is a shrub that can survive in saline environments, has not yet been reported. Here, we first report the genome-wide analysis of the GPX gene family in N. sibirica , leading to a total of seven NsGPX genes that are distributed on six of the twelve chromosomes. Phylogenetic analysis showed that NsGPX genes were grouped into four major groups (Group I-IV). Three types of cis-acting elements were identified in the NsGPX promoters, mainly related to hormones and stress response. The quantitative real-time PCR (qRT-PCR) analysis indicated that NsGPX1 and NsGPX3 were significantly up-regulated in stem and leaf, while NsGPX7 transcriptionally in root in response to salt stress. The current study identified a total seven NsGPX genes in N. sibirica via genome-wide analysis, and discovered that NsGPXs may play an important role in response to salt stress. Taken together, our findings provide a basis for further functional studies of NsGPX genes, especially in regarding to the resistance to salt stress of this halophyte plant N. sibirica , eventually aid in the discovery of new methods to restore overtly saline soil.