One-carbon (C-1) metabolism in response to biotic and abiotic stresses

Abstract

In plants, the generation and supply of methyl units is important in one-carbon (C-1) metabolism, which is essential to all organisms. I have identified a series of cDNA sequences encoding N5, N10-methylenetetrahydrofolate reductase (MTHFR), cobalamin-independent methionine synthase (Met Syn), S-adenosylmethionine synthetase (isoform I, AdoMet Syn2661 and isoform II, AdoMet Syn605), S-adenosylmethionine decarboxylase (SAMDC), serine hydroxymethyltransferase (SHMT) and N5, N10-methenyltetrahydrofolate cyclohydrolase / N5, N10-methylenetetrahydrofolate dehydrogenase (THFC/THFD) in the pathways of generation and supply of methyl units. These are from a cDNA library of mRNA from a susceptible wheat (Triticum monococcum) (Tm) line 441 epidermis, 24 h after inoculation with powdery mildew fungus (Blumeria graminis f. sp. tritici) (Bgt). Phylogenetic tree cluster analysis and subcellular localization prediction by TargetP revealed that MTHFR, Met Syn, AdoMet Syn605, AdoMet Syn2661, SAMDC, and THFC/THFD may be localized in cytosol; SHMT may be localized in mitochondria. Northern blot analysis indicated that expression of MTHFR, Met Syn, AdoMet Syn2661, AdoMet Syn605 and SAMDC genes was up-regulated by powdery mildew infection, abiotic stresses and treatments with stress signal molecules; expression of SHMT and THFC/THFD was either constitutive or down-regulated. These results suggest a close metabolic link between various stresses and the pathways of generation and supply of methyl units in this wheat.