Molecular characterization and regulation of formate dehydrogenase inArabidopsis thaliana

In a previous publication we reported the purification of formate dehydrogenase (FDH, EC 1.2.1.2.) from Arabidopsis thaliana (L.) Heyn. and some of its properties. Here we report the identification of an Arabidopsis FDH cDNA, as well as studies of the molecular characterization and regulation of the enzyme in Arabidopsis. FDH is present as a single-copy gene in the Arabidopsis genome and is located on chromosome V. The deduced amino acid sequence of the Arabidopsis enzyme shows over 80% identity with those from other plants (potato, barley, rice). Northern and western blots show that the FDH mRNA and protein levels in Arabidopsis leaves are similar to those in flowers and stems and higher than those in roots. The effects of chemical and environmental factors on FDH expression in leaves were investigated and compared with their effects on formaldehyde dehydrogenase (FADH, EC 1.2.1.1.). Induction of FDH by one-carbon metabolites, such as methanol, formaldehyde, and formate, was observed at the protein level, but changes at the transcript level were small and different from those observed for FADH. While the steady-state levels of FDH transcripts increased quickly (within hours) and strongly in response to various stresses, protein amounts increased slowly, after 1 to 3 days; FADH transcripts showed no observable change. The possible mechanism of regulation of FDH at both the transcript and protein levels is discussed.Key words: Arabidopsis, formate dehydrogenase, formate metabolism, one-carbon metabolites, stress.