A H2O2-producing glyoxal oxidase is required for filamentous growth and pathogenicity in Ustilago maydis

In the phytopathogenic fungus Ustilago maydis the mating-type loci control the transition from yeast-like to filamentous growth required for pathogenic development. In a large REMI (restriction enzyme mediated integration) screen, non-pathogenic mutants were isolated in a haploid strain that had been engineered to be pathogenic. In one of these mutants, which showed a specific morphological phenotype, the tagged gene, glo1 , was found to encode a product that is highly homologous to a glyoxal oxidase gene from the wood-rot fungus Phanerochaete chrysosporium. Glyoxal oxidase homologues are found in human, plant pathogenic fungi and in plants, but not in other mammals or yeasts. To confirm the function of the glo1 gene, null mutations were generated in compatible haploid U. maydis strains. In crosses null mutants were unable to generate filamentous dikaryons, and were completely non-pathogenic. Using a Glo1-overproducing strain we demonstrated that Glo1 is membrane bound, oxidizes a series of small aldehydes (< C4) and produces H2O2. The enzyme needs to be activated, presumably by auto-oxidation, to show full activity. A potential role for Glo1 during filamentous growth and pathogenic development of U. maydis is proposed.

Regulation and functional expression of cinnamate 4-hydroxylase from parsley

A previously isolated parsley (Petroselinum crispum) cDNA with high sequence similarity to cinnamate 4-hydroxylase (C4H) cDNAs from several plant sources was expressed in yeast (Saccharomyces cerevisiae) containing a plant NADPH:cytochrome P450 oxidoreductase and verified as encoding a functional C4H (CYP73A10). Low genomic complexity and the occurrence of a single type of cDNA suggest the existence of only one C4H gene in parsley. The encoded mRNA and protein, in contrast to those of a functionally related NADPH:cytochrome P450 oxidoreductase, were strictly coregulated with phenylalanine ammonia-lyase mRNA and protein, respectively, as demonstrated by coinduction under various conditions and colocalization in situ in cross-sections from several different parsley tissues. These results support the hypothesis that the genes encoding the core reactions of phenylpropanoid metabolism form a tight regulatory unit.

Differentially regulated NADPH:cytochrome P450 oxidoreductases in parsley

Two NADPH:cytochrome P450 oxidoreductases (CPRs) from parsley (Petroselinum crispum) were cloned, and the complete proteins were expressed and functionally identified in yeast. The two enzymes, designated CPR1 and CPR2, are 80% identical in amino acid sequence with one another and about 75% identical with CPRs from several other plant species. The mRNA accumulation patterns for CPR1 and CPR2 in fungal elicitor-treated or UV-irradiated cultured parsley cells and in developing or infected parsley plants were compared with those for cinnamate 4-hydroxylase (C4H), one of the most abundant CPR-dependent P450 enzymes in plants. All treatments strongly induced the mRNAs for C4H and CPR1 but not for CPR2, suggesting distinct metabolic roles of CPR1 and CPR2 and a functional relationship between CPR1 and C4H.