1887

Abstract

Elsinochromes are nonhost-selective, light-activated, polyketide-derived toxins produced by many phytopathogenic species. We recently showed that the polyketide synthase-encoding gene is essential for elsinochrome biosynthesis in the citrus scab fungus . Sequence analysis beyond the gene identified nine putative ORFs: four genes, designated , , and , all encode polypeptides likely to have biosynthetic or efflux functions; five additional genes, and to , encode hypothetical proteins of unknown function. Northern-blot analysis revealed that expression of these genes in was not completely correlated with accumulation of elsinochromes under nitrogen limitation, alkaline pH or high concentrations of glucose. Targeted disruption of the gene, encoding a putative transcriptional activator, yielded fungal mutants unable to produce elsinochromes, and defective in both conidiation and expression of , , and , whereas expression of , , and was nearly abolished in -disrupted mutants. By contrast, expression of , and was not affected by disrupting either or . Taken together, the results indicate that in addition to polyketide synthase, the products of and other adjacent genes may also play a crucial role in elsinochrome production.

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2008-11-01
2019-10-22
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