The effects of introduction of a fungal glutamate dehydrogenase gene (gdhA) on the photosynthetic rates, biomass, carbon and nitrogen contents in transgenic potato

Abstract

Glutamate dehydrogenase (GDH) catalyzes the reversible amination of 2-oxoglutarate with ammonium to form glutamate. GDH functions in nitrogen assimilation in microorganisms, such as Aspergillus nidulans. However, in plants, glutamine synthetase, not GDH, carries out nitrogen assimilation. Here, we report the effects of introduction of the gdhA gene, encoding NADP(H)-dependent glutamate dehydrogenase, from A. nidulans into potato. We analyzed the resulting changes of photosynthesis, biomass, carbon and nitrogen contents under control and low-nitrogen conditions at the flowering stage and the tuber-bulking stage. There were higher NADP(H)-GDH activities in GDH potato leaves than in the wild type. Regardless of nitrogen conditions, photosynthetic rates and soluble protein concentrations of leaves increased in GDH potatoes at the flowering stage. High photosynthetic rates remained at the tuber-bulking stage in GDH potatoes. The number and dry weight of tubers also increased in GDH potatoes. Under the low-nitrogen condition in particular, carbon and nitrogen contents of GDH potato tubers increased compared with those of the wild type. This resulted from higher rates of carbon and nitrogen redistribution to tuber in GDH potatoes than in wild-type potatoes. Our findings show that the gdhA gene is a powerful tool to increase tuber dry matter and improve efficiency of nitrogen use of potato. © 2012 The Japanese Society for Plant Cell and Molecular Biology.