Transcription factor OsSNAC1 positively regulates nitrate transporter gene expression in rice
Jinfang Qi（杞金芳）, Lu Yu, Jingli Ding, Chenchen Ji, Sheliang Wang, Chuang Wang, Guangda Ding, Lei Shi, Fangsen Xu, Hongmei Cai
Abstract
Nitrogen (N) is a critical factor for crop growth and yield. Improving N use efficiency (NUE) in agricultural systems is crucial for sustainable food production. However, the underlying regulation of N uptake and utilization in crops is not well known. Here, we identified OsSNAC1 (stress-responsive NAC 1) as an upstream regulator of OsNRT2.1 (nitrate transporter 2.1) in rice (Oryza sativa) by yeast 1-hybridization screening. OsSNAC1 was mainly expressed in roots and shoots and induced by N deficiency. We observed similar expression patterns of OsSNAC1, OsNRT2.1/2.2, and OsNRT1.1A/B in response to NO3- supply. Overexpression of OsSNAC1 resulted in increased concentrations of free NO3- in roots and shoots, as well as higher N uptake, higher NUE, and N use index (NUI) in rice plants, which conferred increased plant biomass and grain yield. On the contrary, mutations in OsSNAC1 resulted in decreased N uptake and lower NUI, which inhibited plant growth and yield. OsSNAC1 overexpression significantly upregulated OsNRT2.1/2.2 and OsNRT1.1A/B expression, while the mutation in OsSNAC1 significantly downregulated OsNRT2.1/2.2 and OsNRT1.1A/B expression. Y1H, transient co-expression, and ChIP assays showed OsSNAC1 directly binds to the upstream promoter regions of OsNRT2.1/2.2 and OsNRT1.1A/1.1B. In conclusion, we identified a NAC transcription factor in rice, OsSNAC1, with a positive role in regulating NO3- uptake through direct binding to the upstream promoter regions of OsNRT2.1/2.2 and OsNRT1.1A/1.1B and activating their expression. Our results provide a potential genetic approach for improving crop NUE in agriculture.