Abstract
Rab GTPases are the largest group of the small GTPases family, which play a pivotal role in the secretion of proteins. Arthrobotrys oligospora is a representative nematode-trapping fungus that can produce adhesive networks to capture nematodes. In this study, the roles of two Rab GTPases AoRab-7A and AoRab-2 were characterized by gene knockout in the fungus A. oligospora. The disruption of AoRab-7A hindered the mycelial growth in different media, the conidiation of ΔAoRab-7A transformants was almost abolished, and the transcription of four sporulation-related genes (AbaA, FluG, Hyp1, and VosA) was downregulated compared to the wild-type strain (WT). Furthermore, the tolerance of the ΔAoRab-7A mutants to sodium dodecyl sulfate (SDS) and H2O2 was also significantly reduced compared to the WT, and the transcription of several genes related to environmental resistance, such as genes for catalase and trehalose synthase, was downregulated. Similarly, the extracellular proteolytic activity was decreased. Importantly, the ΔAoRab-7A mutants were unable to produce traps and capture nematodes. However, the disruption of gene AoRab-2 only affected the conidiation slightly but non-significantly, while other phenotypic traits were unaffected. Moreover, the gene AoRab-7A was also involved in the autophagy induced by nitrogen deprivation in A. oligospora. Our results revealed for the first time that the Rab GTPases are involved in the regulation of mycelial growth, conidiation, trap formation, stress resistance, and pathogenicity in the nematode-trapping fungus A. oligospora.
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Acknowledgements
We are grateful to Prof. Jianping Xu of the Dept. of Biology, McMaster University, for his valuable comments and critical discussions.
Funding
The research described here is jointly supported by the NSFC-Yunnan Joint Fund (U1402265), the National Basic Research Program of China (2013CB127503), the National Natural Science Foundation of China (approved nos. 31272093, 31360019, and 31560025), the Program for Excellent Young Talents of Yunnan University (to Jinkui Yang), and the General Program of the Applied Basic Research Programs of Yunnan Province (approval no. 2016FB044).
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Yang, X., Ma, N., Yang, L. et al. Two Rab GTPases play different roles in conidiation, trap formation, stress resistance, and virulence in the nematode-trapping fungus Arthrobotrys oligospora. Appl Microbiol Biotechnol 102, 4601–4613 (2018). https://doi.org/10.1007/s00253-018-8929-1
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DOI: https://doi.org/10.1007/s00253-018-8929-1