Genome-wide Analysis And Functional Identification Of NRT2/3 Gene Family In Barley

Nitrogen is one of the main nutrient elements for plant growth and development.Nearly 90 million tons of nitrogen fertilizer are applied every year all over the world,and the use of nitrogen fertilizer continue to rise,which not only increses the agricultural production costs but also leads to nitrogen pollution in soil surface due to excessive nitrogen fertilizer runs off with rain.Breeding nitrogen-efficient barley varieties is the most effective approach to reduce nitrogen fertilizer application and nitrogen fertilizer pollution.Plants mainly have two transport systems to uptake and transport nitrate nitrogen:high-affinity transport system(HATS)and low-affinity transport system(LATS).Barley is a typical rain-fed crop which mainly absorbs nitrate among different forms of nitrogen.The HvNRT2/3 genes belong to the high-affinity transport system,which can improve the efficiency of nitrate utilization in barley at low-nitrogen concentrations.In this study,the gene structure and chromosomal location of HvNRT2/3 genes were analyzed and molecular phylogenetic tree and expression profiling of HvNRT2/3 genes were constructed by bioinformatics methods.We constructed over-expression vectors of HvNRT2.1/3/5 genes and transformed into arabidopsis to identify their functions.The main results were as follows:1.Ten putative NRT2 and three putative NRT3 genes were identified at the whole genome level of barley.HvNRT2/3 genes were located on 3H,5H,6H and 7H,respectively.Phylogenetic tree revealed that NRT2/3 proteins display clearly divergence between monocot and dicot plants.Tandem repeat contributed to the expansion of the NRT2 gene family in barley.In addition,HvNRT2/3 genes displayed various expression patterns in different tissues and were induced by nitrate in roots.HvNRT2.1/3/5 genes which present higher expression in roots were selected to construct transient expression vectors to inject tobacco.The subcellular localization showed that the HvNRT2.1/3/5 genes were localized on plasma membrane.2.Over-expression vectors of HvNRT2.1/3/5 genes were constructed and transformed into Arabidopsis.Positive lines of single copy were screened to identify the function of HvNRT2.1/3/5 genes.The results showed that the leaves area of HvNRT2.1/3/5 transgenic lines was significantly or extremely significantly increased compared with wild type at seedling stage;the siliques length,seeds per silique,yield per plant nitrate content and total N contents of HvNRT2.1/3/5 transgenic lines were significantly or extremely significantly higher than wide type at mature stage.In addition,siliques per plant of HvNRT2.3 lines and siliques per plant,dry weight per plant of HvNRT2.5 lines were also significantly or extremely significantly than wide type at mature stage In addition,the grain length,grain width,grain area and 1000-grain weight of HvNRT2.1/3/5 transgenic lines were significantly or extremely significantly higher than wild type except for the grain length of HvNRT2.5 lines.Thus,over expression of HvNRT2.1/3/5 may promote the uptake of nitrogen in plants.