Abstract
It is known that the pathogenic fungus, Cochliobolus carbonum, produces HC-toxin, harmful to maize plants. In this respect, maize Hm1 gene confers NADPH-dependent HC-toxin reductase (HCTR) activity which detoxifies HC-toxin. Previously, we isolated YK1 gene from rice possessing 78% amino acid identity to maize HCTR gene. Transgenic rice plants overexpressing YK1 showed tolerance to various stresses. For instance, such plants acquired resistance to rice blast disease and other abiotic stresses such as UV, NaCl, submergence and H2O2 (Uchimiya et al. 2002). Here, we show the evidence that overexpression of YK1 in rice cells promoted the level of NAD(P)(H) through upregulating NAD synthetase activities. Namely, elevated YK1 activity is related to the stimulation of NAD(P)(H) amounts in vivo. Based on this result, we conclude the tight relationship between NAD biosynthesis metabolism and the resistance to ROS stresses.
