Characterization of phosphorus responsive gene(s) under phosphorus application and drought stress treatment in Vigna radiata.

Abstract

Vigna radiata is the third important legume crop. It is a short duration crop with low input requirements. Phosphorus plays an important role in developing the root structures, enhancing the growth of legumes and elevating the nutrient uptake. Phosphorus is an essential macronutrient after nitrogen and is usually present in insufficient quantity in the soil. Fertilizers are applied to which cause many chemical reactions to take place for the plants to absorb phosphate ions. Drought limits the nutrient uptake of a plant, a definitive decline in phosphorus levels has been observed under such conditions. Purple acid phosphatases (PAPs) are the proteins that are having essential role in acclimating plants under phosphorus deficient conditions. They liberate inorganic phosphorus from phosphomonoesters in soil and help in its uptake by the plant. PAP gene family has been previously identified in many plants but their identification in mung bean was not confirmed previously. In the current study, VrPAP gene family was identified in the genome of Vigna radiata on the basis of presence of metallophos superfamily domain and FN3 superfamily domain. The conservation of five conserved motif blocks (DXG/ GDXXY/ GNH(D/E)/ VXXH/ GHXH) were also analysed. On the basis of the conservation pattern, this gene family was divided into three main groups (1,2,3) during the phylogenetic analysis. This categorization was further strengthened by the conserved motif analysis. The results of gene structure were not that conserved throughout each group. Maximum exons reported in a gene were 13 and minimum was 1. According to the gene ontology (GO) annotations, maximum proteins were found to be involved in cellular metabolic processes, dephosphorylation, hydrolase activity, catalase activity, metal ion binding and phosphatase activity. They were located in cellular anatomical entity and in membranes. Results of the expression profiling revealed that the expression of PAP genes increased significantly under low phosphorus, drought and combined conditions of low phosphorus and drought under early, flowering and rewatering stages in both NCM-13 and MSPS-119. The maximum fold change was observed in MSPS-119 under flowering conditions. There was a slight decrease in the expression after rewatering as compared to flowering stage.