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Regulation of subtilisin-like protease prC expression by nematode cuticle in the nematophagous fungus Clonostachys rosea

Authors

  • Cheng-Gang Zou,

    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
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    • These authors contributed equally to this study.

  • Nan Tao,

    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
    2. Institute of Biotechnology, Yunnan Academy of Agricultural Sciences, Kunming, Yunnan 650223, China.
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    • These authors contributed equally to this study.

  • Wen-Jing Liu,

    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
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  • Jin-Kui Yang,

    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
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  • Xiao-Wei Huang,

    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
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  • Xian-Yong Liu,

    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
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  • Hui-Hui Tu,

    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
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  • Zhong-Wei Gan,

    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
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  • Ke-Qin Zhang

    Corresponding author
    1. Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan 650091, China.
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E-mail kqzhang111@yahoo.com.cn; Tel. (+86) 871 5034878; Fax (+86) 871 5033838.

Summary

Nematophagous fungi have been used as biological control agents against nematodes parasitic to plants and animals. These fungi can secret subtilisin-like extracellular serine proteases during the infection of nematodes. The expression of these subtilisin-like serine proteases is regulated by nitrogen sources, including nematode cuticle. However, the mechanisms underlying the nitrogen sources-induced expression of these serine proteases is not well understood. In this study, we investigated the effect of nitrogen sources on the expression of a subtilisin-like extracellular protease, prC, in the nematophagous fungus Clonostachys rosea. Disruption of prC attenuated infection of the fungus to nematodes, indicating that this gene functions as a virulence factor. The inhibition of basal expression of prC by the preferred nitrogen sources (glutamine, ammonia) occurred at the transcriptional level. In contrast, nematode cuticle induced the expression of prC at the post-transcriptional level. The inducible expression of prC by nematode cuticle was significantly suppressed by glutamine, ammonia and phenylmethylsulfonyl fluoride (an inhibitor of serine protease). Thus, the existence of active PrC, albeit at a low level in the medium, is probably essential for further induction of this gene by nematode cuticle. Moreover, the low molecule weight (< 3 kD) degradation products of nematode cuticle could significantly induce the expression of prC. Ammonia suppresses the virulence of C. rosea against nematodes, probably by inhibiting prC expression. Thus, the nematophagous fungi probably could not function well as biocontrol agents in fields fertilized with a large amount of ammonium salt.

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