Formate dehydrogenase in rice plant: Growth stimulation effect of formate in rice plant

NAD-dependent formate dehydrogenase (FDH, EC 1.2.1.2.) plays a key role in the final step of the catabolism of methanol in methylotrophs. In certain p lant species, this enzyme is a mitochondrial and NAD-dependent enzyme. In t his study, the complete cDNA sequence of the rice (Oryza sativa cv Hinohika ri) FDH gene, which contains an open reading frame (ORF) of 1128 bp, was de termined. The sequence corresponds to a protein of 376 amino acids and show s strong homology to the NAD-dependent FDHs from other plants. Our experime ntal results showed that the expression of the rice cDNA in Escherichia col i induced FDH activity, indicating that the cDNA encodes a functional pepti de of FDH. The application of formate to the roots of rice seedlings leads to growth increment both in terms of the length of the aerial part and the fresh weight. The FDH activity and the accumulation of FDH transcripts were strongly enhanced in the root portions of the formate-fed plants. This enh ancement indicates that the transcriptional regulation which responds to fo rmate functions in the rice plant, and that formate can act as an effective inducer for FDH activity.