Abstract
BackgroundThe fungus Colletotrichum gloeosporioides f. sp. aeschynomene produces high levels of indole-3-acetic acid (IAA) in axenic cultures and during plant infection. We generated a suppression subtractive hybridization library enriched for IAA-induced genes and identified a clone, which was highly expressed in IAA-containing medium.ResultsThe corresponding gene showed similarity to oligopeptide transporters of the OPT family and was therefore named CgOPT1. Expression of CgOPT1 in mycelia was low, and was enhanced by external application of IAA. cgopt1-silenced mutants produced less spores, had reduced pigmentation, and were less pathogenic to plants than the wild-type strain. IAA enhanced spore formation and caused changes in colony morphology in the wild-type strain, but had no effect on spore formation or colony morphology of the cgopt1-silenced mutants.ConclusionOur results show that IAA induces developmental changes in C. gloeosporioides. These changes are blocked in cgopt1-silenced mutants, suggesting that this protein is involved in regulation of fungal response to IAA. CgOPT1 is also necessary for full virulence, but it is unclear whether this phenotype is related to auxin.
Highlights
The fungus Colletotrichum gloeosporioides f. sp. aeschynomene produces high levels of indole-3-acetic acid (IAA) in axenic cultures and during plant infection
We previously showed that Colletotrichum gloeosporioides f. sp. aeschynomene (C. gloeosporioides) produces large quantities of IAA in axenic culture [16]
Isolation and characterization of CgOPT1 In search of IAA-induced fungal genes, a suppressive subtraction hybridization (SSH) library was prepared from mycelia grown in media with (+) or without (-) IAA
Summary
The fungus Colletotrichum gloeosporioides f. sp. aeschynomene produces high levels of indole-3-acetic acid (IAA) in axenic cultures and during plant infection. Aeschynomene produces high levels of indole-3-acetic acid (IAA) in axenic cultures and during plant infection. Fungi can produce plant hormones in axenic cultures when supplemented with the appropriate precursors [1]. For production of the hormone indole-3-acetic acid (IAA), tryptophan must be supplied: no IAA is produced without external tryptophan, and the amount of IAA increases with increasing tryptophan concentrations [15]. Various effects of IAA on fungi have been reported. IAA and gibberellic acid were reported to affect yeast sporulation and cell elongation, but the effects of IAA were not uniform and varied according to growth conditions, such as vitamin content in the culture medium [6]. External application of IAA has been shown to have various effects in addi-
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