Reducing expression of a nitrate‐responsive bZIP transcription factor increases grain yield and N use in wheat

Nitrogen (N) plays critical role in plant growth; manipulating N assimilation could be a target to increase grain yield and N use. Here, we show that ABRE‐binding factor (ABF)‐like leucine zipper transcription factor TabZIP60 mediates N use and growth in wheat. The expression of TabZIP60 is repressed when the N‐deprived wheat plants is exposed to nitrate. Knock down of TabZIP60 through RNA interference (RNAi) increases NADH‐dependent glutamate synthase (NADH‐GOGAT) activity, lateral root branching, N uptake and spike number, and improves grain yield more than 25% under field conditions, while overexpression of TabZIP60‐6D had the opposite effects. Further investigation shows TabZIP60 binds to ABRE‐containing fragment in the promoter of TaNADH‐GOGAT‐3B and negatively regulates its expression. Genetic analysis reveals that TaNADH‐GOGAT‐3B overexpression overcomes the spike number and yield reduction caused by overexpressing TabZIP60‐6D. As such, TabZIP60‐mediated wheat growth and N use is associated with its negative regulation on TaNADH‐GOGAT expression. These findings indicate that TabZIP60 and TaNADH‐GOGAT interaction plays important roles in mediating N use and wheat growth, and provides valuable information for engineering N use efficiency and yield in wheat.