Heterologous expression of fungal AcGDH alleviates ammonium toxicity and suppresses photorespiration, thereby improving drought tolerance in rice.

ABSTRACT

Drought stress can significantly affect plant growth and agricultural productivity. Thus, it is essential to explore and identify the optimal genes for the improvement of crop drought tolerance. Here, a fungal NADP(H)-dependent glutamate dehydrogenase gene (AcGDH) was isolated from Aspergillus candidus, and heterologously expressed in rice. AcGDH has a high affinity for NH4+ and increases the ammonium assimilation in rice. AcGDH transgenic plants exhibited a tolerance to drought and alkali stresses, and their photorespiration was significantly suppressed. Our findings demonstrate that AcGDH alleviates ammonium toxicity and suppresses photorespiration by assimilating excess NH4+ and disturbing the delicate balance of carbon and nitrogen metabolism, thereby improving drought tolerance in rice. Moreover, AcGDH not only improved drought tolerance at the seedling stage but also increased the grain yield under drought stress. Thus, AcGDH is a promising candidate gene for maintaining rice grain yield, and offers an opportunity for improving crop yield under drought stress.