Mutation of FVS1, encoding a protein with a sterile alpha motif domain, affects asexual reproduction in the fungal plant pathogen Fusarium oxysporum

Authors

  • Yuichiro Iida,

    Corresponding author
    1. Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan
    Current affiliation:
    1. National Institute of Vegetable and Tea Science, Mie, Japan
    • Correspondence: Yuichiro Iida, National Institute of Vegetable and Tea Science, Mie 514-2392, Japan. Tel.: +81 59 268 1331; fax; +81 59 268 1339; e-mail: y_iida@affrc.go.jp

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  • Kazuki Fujiwara,

    1. Graduate School of Environment Study, Nagoya University, Chikusa, Nagoya, Japan
    2. National Institute of Vegetable and Tea Science, Mie, Japan
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  • Yosuke Yoshioka,

    1. National Institute of Vegetable and Tea Science, Mie, Japan
    Current affiliation:
    1. University of Tsukuba, Tsukuba, Japan
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  • Takashi Tsuge

    1. Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan
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Abstract

Fusarium oxysporum produces three kinds of asexual spores: microconidia, macroconidia and chlamydospores. We previously analysed expressed sequence tags during vegetative growth and conidiation in F. oxysporum and found 42 genes that were markedly upregulated during conidiation compared to vegetative growth. One of the genes, FVS1, encodes a protein with a sterile alpha motif (SAM) domain, which functions in protein–protein interactions that are involved in transcriptional or post-transcriptional regulation and signal transduction. Here, we made FVS1-disrupted mutants from the melon wilt pathogen F. oxysporum f. sp. melonis. Although the mutants produced all three kinds of asexual spores with normal morphology, they formed markedly fewer microconidia and macroconidia than the wild type. The mutants appeared to have a defect in the development of the conidiogenesis cells, conidiophores and phialides, required for the formation of microconidia and macroconidia. In contrast, chlamydospore formation was dramatically promoted in the mutants. The growth rates of the mutants on media were slightly reduced, indicating that FVS1 is also involved in, but not essential for, vegetative growth. We also observed that mutation of FVS1 caused defects in conidial germination and virulence, suggesting that the Fvs1 has pleiotropic functions in F. oxysporum.

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