Screening Of High Nitrogen Use Efficiency Varieties Of Ramie (Boehmeria Nivea L.) And Analysis Of Expression On BnNRT1.1

In order to speed up the process of breeding ramie varieties with high nitrogen use efficiency and improve the utiliation rate of nitrogen and explore the molecular mechanism of high efficiency utilization of nitrate in Ramie,in this study,a pot experiment was conducted to study the effects of different propagation materials and fertilization methods on nitrogen utilization rate of ramie.In addition,thirtyfive varieties of ramie in the core Ramie Germplasm nursery were selected as the research objects.As a result,two varieties with high nitrogen use efficiency and two varieties with low nitrogen use efficiency were screened by water culture and pot experiments respectively.The full-length cDNA sequence of ramie BnNRT1.1 gene was cloned and done bioinformatics analysis.Meanwhile,the expression of BnNRT1.1 in different parts of ramie varieties with different nitrogen use efficiency was clarified by qRT-PCR expression analysis in Longtan dama and Qingpi ganma.The results showed that:(1)The nitrogen use efficiency of ramie was related to the breeding material and the harvest times.The nitrogen accumulation of the cuttage seedlings was significantly higher than that of the seedlings after the first harvest time,while was significantly lower than that of the seedlings after the second harvest time.(2)The nitrogen use efficiency of ramie is related to the method of fertilization.It was higher under the condition of root fertilization than foliar fertilization in the same variety of ramie except Zhongzhu No.1.Under the two fertilization conditions,Zhongzhu No.1 was the variety with high nitrogen use efficiency.(3)There were some differences between results of hydroponic and pot screening test.Combied two screening test results,T31(Longtan hemp),T13(1296)with high nitrogen use efficiency and T21(Qingpi ganma),T15(Mengheng Qingma)with low nitrogen use efficiency were obtained.There was a great difference in nitrogen utilization between them.(4)BnNRT1.1 gene was cloned,containing 1869 bp,including open reading frame(1776 bp)and encoding 591 amino acids.(5)The results of bioinformatics analysis showed that the protein molecular weight of BnNRT1.1 was 65.25 kD and the isoelectric point was 8.85 and it was a hydrophobic protein with 12 transmembrane domains and 15 phosphorylation sites.It had important functions in signal transduction and metabolism of nitrogen translocation.Phylogenetic analysis showed that BnNRT1.1 gene of ramie was homologous with Prunus avium,Pyrus x bretschneideri and Morus notabilis.(6)Expression characteristics analysis of qRT-PCR showed that BnNRT1.1 was mainly expressed in roots of ramie.But it was relatively low in stems and leaves.Nitrate induction treatment showed that the expression of BnNRT1.1 in Longtan dama with high nitrogen use efficiency was higher than that in Qingpi ganma with low nitrogen use efficiency and the expression reached the maximum after treatment three days.The results of this study provided reliable materials for the breeding of ramie varieties with high nitrogen efficiency and preliminarily revealed its molecular mechanism utilization of nitrate uptake.Also,the molecular mechanism of BnNRT1.1 for absorption,transportion and regulation of nitrate was preliminarily described in order to improve the nitrogen use efficiency of ramie.