Genome-wide identification and functional analysis of denitrosylases (S-nitrosoglutathione reductases and NADPH-dependent thioredoxin reductases) in Brassica juncea.

S-nitrosylation is a well-known post-translational modification that modulates nitric oxide-dependent cell signaling. NADH-dependent S-nitrosoglutathione reductase (GSNOR) and NADPH-dependent thioredoxin reductase (NTR) enzymes are essential for nitric oxide/S-nitrosothiol (NO/SNO) homeostasis. GSNOR and NTR regulate denitrosylation by reducing S-nitrosoglutathione (GSNO) and thioredoxins, respectively. Genome-wide identification yielded 4 GSNOR and 12 NTR (4 each of NTRA, NTRB, and NTRC) genes in Brassica juncea. Syntenic relationship showed whole genome triplication (WGT) and tandem duplications. The phylogenetic analysis revealed clustering of BjGSNORs and BjNTRs with Arabidopsis homologs suggesting high sequence similarity within groups. Subcellular localization prediction suggested BjGSNOR localizes not only to the cytosol, but also to the Golgi apparatus and endoplasmic reticulum. BjNTRA and BjNTRB were localized in the cytoplasm and mitochondria, respectively, whereas BjNTRC localized in the chloroplast and nucleus. Several cis-acting elements involved in light responsiveness and expression analysis suggested the regulation of denitrosylation by light. The analysis of the promoter region also showed various phytohormone-regulated elements, suggesting the involvement of these enzymes in plant growth. Furthermore, GSNOR and NTR activities were higher in early growth stages. Differential spatial distributions of both the enzymes were observed with higher activity in hypocotyl in comparison with roots and cotyledons of the seedling. In flower, the highest activities were observed in carpel and least in stamens. Collectively, these findings provide an understanding of the structure, localization, and evolution of multiple copies of denitrosylases BjGSNOR and BjNTR, along with their possible roles in plant development. [ABSTRACT FROM AUTHOR]