Applied Microbiology and Biotechnology

, Volume 102, Issue 10, pp 4577–4588 | Cite as

The bZIP transcriptional factor activator protein-1 regulates Metarhizium rileyi morphology and mediates microsclerotia formation

  • Zhangyong Song
  • Youping Yin
  • Yunlong Lin
  • Fang Du
  • Guangwei Ren
  • Zhongkang Wang
Applied genetics and molecular biotechnology


Internal oxidative stress can trigger microsclerotia (MS) formation of Metarhizium rileyi in liquid culture. Activator protein 1 (AP1) is a transcription factor and an important determinant of the response to oxidative stress. To investigate how M. rileyi responds to internal oxidative stress and how MS development is regulated, the Mrap1 gene was characterized. Mrap1 was highly expressed during periods of invasive hyphal growth and in response to changing culture conditions during MS development. Compared with the wild-type and complemented strains, ΔMrap1 mutants exhibited various defects in aerial hyphal growth, yeast-to-hypha transition, and conidia and MS formation. ΔMrap1 mutants also displayed sensitivity to oxidative stress, were morphologically abnormal, and responded differently to oxidative stress during MS development. ΔMrap1 mutants had significantly reduced conidial (74–82%) and MS (99%) yields. Insect bioassays revealed that ΔMrap1 mutants displayed reduced virulence in topical (43–76%) and injection (45–70%) bioassays. Moreover, the ability of ΔMrap1 mutants to grow out of the cuticle was reduced due to impaired conidiation on the host cadaver. Digital gene expression profiling revealed that genes involved in antioxidation, pigment biosynthesis, and ion transport were regulated by Mrap1 during MS development. Taken together, our results confirm the importance of Mrap1 in vegetative growth, conidia and MS formation, and virulence.


Microsclerotia Metarhizium rileyi Morphology Activator protein-1 Digital gene expression 



This research was supported financially by the National Science Foundation of the People’s Republic of China (No. 31701127; No. 31570073), Educational Commission of Sichuan Province of China (18ZA0515), and Major Special Projects (No.110201601023(LS-03)).


This research was funded by the National Science Foundation of the People’s Republic of China (No. 31701127; No. 31570073), Educational Commission of Sichuan Province of China (18ZA0515), and Major Special Projects (No.110201601023(LS-03)).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical statement

This article does not contain any studies with human participants by any of the authors.

Supplementary material

253_2018_8941_MOESM1_ESM.pdf (1.5 mb)
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© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Basic Medical SciencesSouthwest Medical UniversityLuzhouPeople’s Republic of China
  2. 2.Chongqing Engineering Research Center for Fungal Insecticide, School of Life ScienceChongqing UniversityChongqingPeople’s Republic of China
  3. 3.Institute of Qingdao Economic Crop Chinese Academy of Agricultural SciencesQingdaoPeople’s Republic of China

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