Auxin promotes nitrate uptake by upregulating AtNRT1.1 gene transcript level in Arobidopsis thaliana

In order to study the mechanisms of the effects of auxin signaling pathway on nitrate uptake, scanning ionselective electrode technique(SIET) and quantitative realtime PCR technique were used to determine net plasma membrane NO-3 fluxes and the expression of nitrate transporter AtNRT1.1 in primary roots of Arabidopsis thaliana wild type Col-0, auxin overproducing mutant yuc1-D, and auxin insensitive mutant axr1-12. Moreover, we examined net plasma membrane NO-3 fluxes and the expression of AtNRT1.1 in primary roots of Col-0 and dual-affinity nitrate transporter mutant nrt1.1 seedlings under the normal condition(CK), the treatment with exogenous IAA or the treatment with the auxin efflux inhibitor 2.3.5triidobenzoid acid (TIBA). The nitrate uptake and AtNRT1.1 gene transcript level in yuc1-D seedlings were remarkably enhanced, whereas those in axr1-12 seedlings declined compared with Col-0 seedlings. The exogenous IAA treatment enhanced nitrate uptake and AtNRT1.1 gene transcript level in Col-0 seedlings, while the TIBA treatment had an opposite effect. Furthermore, the differences of nitrate uptake and AtNRT1.1 gene transcript level in nrt1.1 seedlings among CK, IAA and TIBA treatments were insignificant compared with Col-0 seedlings, revealing the important role that AtNRT1.1 gene played in nitrate uptake pathway response to auxin.