Over-Expressing And Silencing The Gene Tanrt2.1 Of Winter Wheat (Triticum Aestivum L.) Affected The Growth And Nitrogen Uptake Of Plants

In order to investigate the nitrate uptake function of the nitrate transporter（NRT）gene TaNRT2.1 and its partner protein TaNAR2.1 in winter wheat,on the one hand,vectors either overexpressing TaNRT2.1 singly or double overexpressing TaNRT2.1 andTaNAR2.1 were transformed into Arabidopsis thaliana using Agrobacterium mediated floral dip method.Homozygotes lines of the transformed Arabidopsis plants were screened using Hygromycin and PCR.Nitrogen（N）uptake dynamics and the total N content in the shoots of Arabidopsis homozygotes were measured;on the other hand,the effect of silencing TaNRT2.1 on the growth and N uptake of wheat was studied using virus-induced gene silencing（VIGS）method.The following are the main results:1.Neither over-expressing TaNRT2.1 nor over-expressing both of TaNRT2.1 and TaNAR2.1 could increase the nitrate uptake rates of transgenic Arabidopsis plant in the low nitrate concentration(<1 mmol·L^-1).Over-expressing TaNRT2.1+TaNAR2.1 significantly increased the nitrate uptake rates compared to the wild-type Arabidopsis plants in the high nitrate concentration(>1 mmol·L^-1).The maximum¹⁵NO₃^-uptake rate of Arabidopsis plants over-expressing TaNRT2.1+TaNAR2.1 was higher than that of wild-type plants and plants over-expressing TaNRT2.1.2.In the low nitrate concentration(0.1 mmol·L^-1),the growth and total N uptake of the transgenic Arabidopsis plants were not different from that of the wild-type plants.In the high nitrate concentration(10 mmol·L^-1),the transgenic Arabidopsis plants grew better than the wild-type plants.Over-expressing TaNRT2.1 singly only increased the siliques dry weight and shoot biomass of Arabidopsis.But over-expressing TaNRT2.1+TaNAR2.1significantly increased the shoot biomass,root biomass and total N uptake in Arabidopsis plants.3.BSMV-VIGS can silence the expression of the gene TaNRT2.1 in the roots of wheat.There were differences in leaf phenotypes,TaNRT2.1 gene expression levels,biomasses,and total N uptake among different wheat varieties after inoculation with virus.The degree of gene silence in roots of wheat differed between the low nitrogen(0.1 mmol·L^-1)and high nitrogen(15 mmol·L^-1)conditions.The shoot biomass,total biomass,N concentration and the total N uptake of all the five different wheat varieties were not influenced by gene silencing under low N conditions.The shoot biomass and total N uptake of the variety LuoMai 1 were significantly decreased by gene silencing under the high N conditions.Gene silencing did not influence the shoot biomass and total N uptake of other 4 wheat varieties under high N conditions.4.The total¹⁵N content and root¹⁵N uptake rate were decreased significantly by gene silencing under the low(0.1,0.5 mmol·L^-1)N conditions in the variety LuoMai 1,but were not influenced by gene silencing under the high(5.0,10.0 mmol·L^-1)N conditions.We concluded that TaNRT2.1 in roots of winter wheat can transport NO₃^-.Over-expressing TaNRT2.1+TaNAR2.1 performed better than over-expressing TaNRT2.1 singly in improving the growth and N uptake of Arabidopsis,although over-expression TaNRT2.1singly can also increase the total N uptake of Arabidopsis.The silencing of TaNRT2.1 can decrease the N uptake rate of wheat suggesting that TaNRT2.1 plays an important role in regulating nitrogen uptake of wheat.