In silico characterization of a nitrate reductase gene family and analysis of the predicted proteins from the moss physcomitrella patens

Abstract

Assimilatory nitrate reductase (NR; EC 1.7.1.1-3) catalyzes the reduction of nitrate to nitrite. This enzyme has a conserved structure common to fungi, algae and plants. However, some differences in the amino acid sequence between plant and algal NR suggest that the activity regulation mechanisms have changed during plant evolution. Since only NR s from angiosperms have been studied, the search and analysis of NR genes and proteins from the moss Physcomitrella patens, a basal land plant, was performed to widen the knowledge of land plant NR structure. A family of three nr genes, named ppnia1;1, ppnia1;2 and ppnia2, was localized in the P. patens genome. The predicted proteins are canonical NR s with the conserved domains Molybdene-Cytochrome b-Cytochrome b reductase and possess 20 amino acid residues important for the enzymatic function conserved in plant and algal NR s. Interestingly, moss NR s lack a consensus sequence, common to angiosperm NR s, that is a target for posttranslational regulation. A phylogenetic tree with embryophyte and green algae NR sequences was constructed and P. patens NR s localized at the base of embryophyte NR evolution. The data presented here suggest that bryophytes and vascular plants have different systems to regulate NR activity. © 2012 Landes Bioscience.