NRT2.1 mediates the reciprocal regulation of nitrate and NO/SNO in seedling leaves of Fraxinus mandshurica and Betula platyphylla

Nitric oxide (NO) and S-nitrosothiol (SNO) are signal molecules and the products of nitrogen metabolism. Nitrate (NO 3 − ) is the main nitrogen source, and nitrate transporters (NRTs) are responsible for NO 3 − absorption or transport. However, the interactive effect between NO 3 − /NRT and NO/SNO in tree plants remains ambiguous. In the present study, 25 mmol L −1 NO 3 − and 1 mmol L −1 NO donor sodium nitroprusside (SNP) treatment that was conducted for 24 h enhanced NO/SNO and NO 3 − metabolism, whereas 2.5 mmol L −1 NO 3 − and 80 μmol L −1 N6022 (a compound that increases SNO content) treatment reduced them in seedling leaves of Fraxinus mandshurica and Betula platyphylla . Among the nine NRT family members examined, the gene expression level of NRT2.1 had a greater response to NO/SNO and NO 3 − treatment in the seedling leaves of F. mandshurica and B. platyphylla . Meanwhile, FmNRT2.1 mediated NO and SNO production in seedling leaves of F. mandshurica using Agrobacterium -mediated transient transformation. These findings shed light on the reciprocal regulation between NO 3 − and NO/SNO in seedlings of F. mandshurica and B. platyphylla , and NRT2.1 may act as a key regulatory hub.