Cloning And Expression Characteristics Of Nitrate Transporter LcNRT1.1,LcNRT1.2 And LcNRT1.7 Genes From Leymus Chinensis

Nitrogen is an important component of plant tissues and organs,which is essential for plant growth and yield formation.As the main nitrogen source of most plants,NO₃^-uptake and transport are accomplished by nitrate transporters.NRT 1.1,NRT 1.2 and NRT 1.7 are important members of the NRT gene family.They not only participate in the process of nitrogen uptake,transport and reuse,but also play an important role in plant response to drought and other stresses.Leymus chinensis is one of the most important grassland species in northern China.Because of its long-term living in arid,cold and barren environment,it contains rich genetic resources of barren and stress resistance.Therefore,cloning the above genes from Leymus chinensis will not only provide the basis for revealing the molecular regulation mechanism of nitrogen uptake and transport,but also provide important support for cultivating nitrogen efficient utilization and stress-resistant plants.The full-length sequences of LcNRT1.1,LcNRT 1.2 and LcNRT 1.7 genes of Leymus chinensis were obtained by RT-PCR using the genome and transcriptome sequencing data of Leymus chinensis Jisheng 4.Then LcNRT 1.1,LcNRT 1.2 and LcNRT 1.7 were analyzed by bioinformatics software to predict the primary structure,secondary structure and tertiary structure of each gene encoding protein,as well as the hydrophilic/hydrophobic and transmembrane domains of corresponding proteins.LcNRT 1.1,LcNRT 1.2 and LcNRT 1.7 in Leymus chinensis were studied and analyzed in different tissues,different growth stages,diurnal changes and different nitrogen levels.The main conclusions are as follows:?1?The full-length sequences of LcNRT 1.1,LcNRT 1.2 and LcNRT 1.7 genes of Leymus chinensis were 1812 bp,1803 BP and 1824 bp,respectively.The corresponding coding amino acids were 597,545 and 625,respectively.The secondary structures of LcNRT 1.1,LcNRT 1.2 and LcNRT 1.7 protein all contain alpha-helix,extension chain and Random coin,and no signal peptide exists.LcNRT1.1 and LcNRT1.2 proteins of Leymus chinensis have 12 transmembrane regions,and NRT1.7 proteins have 11 transmembrane regions.LcNRT 1.1 and LcNRT 1.7 are hydrophobic proteins and LcNRT 1.2 are hydrophilic proteins.LcNRT 1.1,LcNRT 1.2 and LcNRT 1.7 proteins may be membrane proteins located on the plasma membrane.Leymus chinensis LcNRT 1.1 has high homology with AtNPF4.5 and Zm NRT 1.1,while LcNRT 1.2 has high homology with at NPF4.5,DcNRT 1.7 of Dendrobium candidum and OsNRT 1.2 of rice;Leymus chinensis LcNRT 1.7 has high homology with at NRT 1.7,at NRT 1.7 of Arabidopsis thaliana and Dendrobium candidum DcNRT 1.7.?2?The relative expression levels of LcNRT 1.1,LcNRT 1.2 and LcNRT 1.7 in Leymus chinensis were different in different periods and tissues,and they were regulated by day and night alternately.The expression levels of LcNRT 1.1 and LcNRT 1.7 have different characteristics in nitrate and ammonium nitrogen.After nitrogen depletion,nitrate nitrogen could induce LcNRT 1.1 and LcNRT 1.7 genes in Leymus chinensis roots,while ammonium nitrogen could inhibit the expression of LcNRT 1.1 and LcNRT 1.7.Low concentration of ammonium nitrogen could induce the expression of LcNRT 1.1 and LcNRT 1.7 in different ratios of ammonium and nitrate,and the overall change trend of LcNRT 1.1 and LcNRT 1.7 expression in Leymus chinensis roots was 0:100>25:75>50;50.The expression of LcNRT1.1 and LcNRT1.7 in Leymus chinensis root was higher than 25:75 in the treatment of 25:100 ammonium-nitrate ratio,LcNRT1.1 and LcNRT1.7 in the treatment of 0:100ammonium-nitrate ratio and 25:100 in the treatment of 0:100 ammonium-nitrate ratio.