Molecular characterization and regulation of formate dehydrogenase in Arabidopsis thaliana

In a previous publication we reported the purification of formate dehydroge nase (FDH, EC 1.2.1.2.) from Arabidopsis thaliana (L.) Heyn. and some of it s 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 Arabido psis genome and is located on chromosome V. The deduced amino acid sequence of the Arabidopsis enzyme shows over 80% identity with those from other pl ants (potato, barley, rice). Northern and western blots show that the FDH m RNA and protein levels in Arabidopsis leaves are similar to those in flower s and stems and higher than those in roots. The effects of chemical and env ironmental factors on FDH expression in leaves were investigated and compar ed with their effects on formaldehyde dehydrogenase (FADH, EC 1.2.1.1.). In duction of FDH by one-carbon metabolites, such as methanol, formaldehyde, a nd formate, was observed at the protein level, but changes at the transcrip t level were small and different from those observed for FADH. While the st eady-state levels of FDH transcripts increased quickly (within hours) and s trongly in response to various stresses, protein amounts increased slowly, after 1 to 3 days; FADH transcripts showed no observable change. The possib le mechanism of regulation of FDH at both the transcript and protein levels is discussed.