Genome-wide identification of NTRs in peanut and functional profiling of AhNTR2-2 in response to salt and heat stress as a negative regulator.

Peanut (Arachis hypogaea) is an important oil crop cultivated on a large scale throughout the world. However, the molecular mechanisms underlying peanut responses to stresses are largely unknown. NADPH-dependent thioredoxin reductases (NTRs) belong to a superfamily of flavoprotein disulfide oxidoreductases, with a variety of functions. In this study, a total of five NTR members were identified. On the basis of their phylogenetic relationships and gene structure, the AhNTR genes are classified into two categories: AhNTR2 (NTRA/B) and AhNTR3 (NTRC). Members within the same group had similar motif compositions and gene structure. The promoter sequences of AhNTR genes contain multiple cis-acting elements associated with stress response, phytohormone signal transduction and plant growth and development. AhNTR2-2 is highly expressed in leaves and roots, with the greatest number of stress- and phytohormone-responsive cis-acting elements in the promoter, thus, it was selected for further research. Subcellular assays revealed that AhNTR2-2 is a mitochondrial protein that responds to NaCl stress. The overexpression of AhNTR2-2 in Arabidopsis conferred sensitivity to NaCl and heat stresses via reducing antioxidant enzyme activities and ROS accumulation. AhNTR2-2 interacts with AhTRX h2. The effects of AhTRX h2 overexpression in Arabidopsis were similar to those of stress. Furthermore, an interaction between AhTRX h2 and AhGSNOR1 was identified. AhNTR2-2 and AhTRX h2 constitute an S-nitrosylated NTR-TRX system in peanut. Our findings provide a foundation for a comprehensive analysis of the AhNTR family.