Sequence of a cDNA from Oryza sativa (L.) encoding the pyruvate decarboxylase 1 gene.

PDC (EC 4.1.1.1) is the first enzyme of the branch glycolytic pathway that together with ADH (EC 1.1.1.1) converts pyruvate to ethanol under anaerobic conditions. This pathway, which produces ATP by substrate-leve1 phosphorylation, is important for the survival of plants that experience hypoxic or anoxic conditions that occur when plants are submerged during flooding. PDC and ADH, along with severa1 other glycolytic enzymes, show anaerobic induction in plant tissues (Laszlo and St. Lawrence, 1983; Bailey-Serres et al., 1988; Kelly, 1989; Xie and Wu, 1989; Waters et ai., 1991), and concomitantly with the induction of PDC and ADH, increased production of ethanol has been reported (Waters et al., 1991; Good and Muench, 1993). It has been suggested that plants under submergence conditions experience a shortage of oxygen because gas diffuses 10,000 times more slowly in water than in air (Armstrong, 1979). Because of the shortage of oxygen, ATP production via oxidative phosphorylation diminishes, and the only means for the plants to convert sugars into ATP is via lactic acid or ethanolic fermentation. In plants ethanolic fermentation appears to be the major mechanism for providing energy and thus conferring tolerance to plant tissues to anoxia (Waters et al., 1991; Good and Muench, 1993). High rates of alcoholic fermentation conferring high tolerance to anoxia in maize have been shown in previous studies (Saglio et al., 1988; Johnson et al., 1989). It has also been suggested that alcoholic fermentation is usually rate limited by PDC (Waters et al., 1991). Increasing alcoholic fermentation by upregulating PDC and possibly ADH to provide greater levels of ATP for various biosynthetic reactions may be one way of altering plant metabolism to provide tolerance to flooding. pdc genes have been isolated from maize (Kelly et al., 1991; Peschke and Sachs, 1993), yeast (Kellerman et al., 1986), and bacteria (Conway et al., 1987). In this communication we report the isolation of the p d c gene from a cDNA library constructed from anaerobically treated suspension cells of the rice variety, IR54 (Table I). We have designated this gene as rice pdc 1 gene because we have isolated multiple p d c genes from rice.