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

Abstract

Nitrogen is an important nutrient for the growth and yield of wheat. However, in practical production, wheat suffers from nitrogen stress. In this study, we generated wheat plants with improved low nitrogen (LN) tolerance by introducing AtbZIP69, a gene encoding a basic leucine zipper domain transcription factor, into the wheat variety Shi 4056. We observed that AtbZIP69 expression in transgenic wheat was induced by LN and drought stress. AtbZIP69 localised in the nucleus and activated transcription. A greenhouse trial revealed that, compared to wild type (WT) wheat, the AtbZIP69 transgenic wheat showed significantly increased drought and LN stress tolerance. A two-year field trial demonstrated that the yield and number of spikes of transgenic wheat were significantly higher than those of WT wheat under LN conditions. By investigating nitrogen use-related traits, we discovered that overexpression of AtbZIP69 altered nitrogen distribution by allocating more nitrogen to grains under LN conditions. In addition, the expression of nitrogen transporter protein genes (such as TaNRT2.1, TaNRT2.5, and TaNR1) was higher in AtbZIP69 transgenic wheat than in WT wheat under LN conditions. Overall, AtbZIP69 overexpression increased nitrogen content of the transgenic line 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 using heterologous expression analysis of wheat.

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