Glutathione-dependent formaldehyde dehydrogenase/GSNO reductase from Arabidopsis.Expression pattern and functional implications in phytoremediation and pathogenesis

The glutathione-dependent formaldehyde dehydrogenase (FALDH) is the main enzyme of the formaldehyde detoxification system in eukaryotes. In Arabidopsis FALDH is coded by a single gene, which is constitutively expressed [1]. By immunolocalization experiments on Arabidopsis root and leaf sections, we demonstrate that the pattern of expression of the enzyme is cell specific. By using tobacco BY-2 cell cultures we show that FALDH co-localizes with tubulin on the cortical microtubules and the microtubules figures (preprophase band, mitotic spindle and phragmoplast), which suggests a role for FALDH in some plant-specific function during cell division. Overexpression of FALDH in Arabidopsis plants results in a 25% increase in the efficiency of elimination of exogenous formaldehyde, whereas plants with reduced levels of FALDH, bearing antisense constructs, show a reduced ability and slower rate in formaldehyde elimination [2]. These results confirm the central role of FALDH in formaldehyde metabolism in plants and have important implications in the phytoremediation of environmental formaldehyde.

The importance of FALDH has been greatly increased by the discovery of its potent activity toward S-nitrosoglutathione, the condensation product of glutathione and nitric oxide (NO) [3–5]. NO and NO-related metabolites, such as S-nitrosothiols (SNOs) play a central role in signal transduction and host defense [6]. We have investigated the gene response to mechanical wounding and plant hormones involved in the signal transduction pathway, showing that the gene is down-regulated by wounding in a JA-dependent pathway, and that it is transcriptionally activated by salicylic acid [7]. This is the first time that regulation of FALDH in response to signals associated with plant defense has been demonstrated.