Overexpression of Atbzip69 Gene Confers Tolerance to Nitrogen Stress and Increases Field Yield in Transgenic Wheat

Abstract

Nitrogen is an important nutrients of growth and yield in wheat, however, the excessive application of fertilizer has exerted a great threat on the environment. Therefore, it is crucial to enhanced nitrogen use efficiency (NUE), but only few related genes have been researched in field crops. In this study, we generated wheat plants showing improved low nitrogen (LN) tolerance, by introducing AtbZIP69, a gene encoding a bZIP transcription factor, into Shi 4056. We found that AtbZIP69 in transgenic wheat was induced by LN and drought. AtbZIP69 is localized in the nucleus and activates transcription. The greenhouse trial revealed that compared to the wild type (WT), the AtbZIP69 transgenic lines showed significantly increased drought and LN stress tolerance. A two-year field trial demonstrated that the yield and number of spikes of transgenic lines was significantly higher than the WT under LN conditions. By investigating N-use-related traits, we discovered that overexpression of AtbZIP69 altered N distribution by allocating more N to grains under LN conditions. In addition, the expression of N transporter protein genes (e.g. TaNRT2.1, TaNRT2.5, TaNR1) was higher in AtbZIP69 transgenic lines than in WT under LN. Overall, AtbZIP69 overexpression increased the nitrogen content of transgenic lines grains under LN conditions by regulating the expression of nitrogen-related transporter protein genes, potentially leading to increased grain yield. As a result, a new candidate gene for improving LN stress tolerance in the field was identified with the use of wheat heterologous expression analysis.

Keywords: bZIP transcription factors, low nitrogen stress, nitrogen use efficiency, grain yield, transgenic wheat