The Msn2 Transcription Factor Regulates Acaricidal Virulence in the Fungal Pathogen Beauveria bassiana .

Autor:	Muniz ER; Escola de Veterinária e Zootecnia, Universidade Federal de Goiás, Goiânia, Brazil.; Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Brazil., Ribeiro-Silva CS; Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Brazil., Arruda W; Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Brazil., Keyhani NO; Department of Microbiology and Cell Science, University of Florida, Gainesville, FL, United States., Fernandes ÉKK; Escola de Veterinária e Zootecnia, Universidade Federal de Goiás, Goiânia, Brazil.; Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Brazil.
Jazyk:	angličtina
Zdroj:	Frontiers in cellular and infection microbiology [Front Cell Infect Microbiol] 2021 Jul 20; Vol. 11, pp. 690731. Date of Electronic Publication: 2021 Jul 20 (Print Publication: 2021).
DOI:	10.3389/fcimb.2021.690731
Abstrakt:	Beauveria bassiana holds promise as a feasible biological control agent for tick control. The B. bassiana stress-response transcription factor Msn2 is known to contribute to fungal growth, conidiogenesis, stress-response and virulence towards insects; however, little is known concerning whether Msn2 is involved in infection across Arthropoda classes. We evaluated the effects of Msn2 on B. bassiana virulence against Rhipicephalus microplus (Acari, Ixodidae) using wild-type, targeted gene knockout ( ΔBbmsn2 ) and complemented mutant ( ΔBbmsn2/Bbmsn2 ) strains. Reproductive parameters of R. microplus engorged females treated topically or by an intra-hemocoel injection of conidial suspensions were assessed. Treated cuticles of engorged females were analyzed by microscopy, and proteolytic activity of B. bassiana on cuticles was assessed. Topically treated engorged females showed high mean larval hatching (>84%) in control and ΔBbmsn2 treatments, whereas treatment with the wild-type or ΔBbmsn2/Bbmsn2 strains resulted in significantly decreased (lowered egg viability) larval hatching. Percent control of R. microplus topically treated with ΔBbmsn2 was lower than in the groups treated with wild-type (56.1%) or ΔBbmsn2/Bbmsn2 strains. However, no differences on reproductive parameters were detected when R. microplus were treated by intra-hemocoel injection using low (800 conidia/tick) doses for all strains tested; R. microplus injected with high doses of wild-type or mutant strains (10 6 conidia/tick) died before laying eggs (~48 h after treatment). SEM analyses of B. bassiana infection showed similar conidial germination and formation of pseudo-appressoria on tick cuticle. Histological sections of ticks treated with the wild-type or ΔBbmsn2/Bbmsn2 strains showed fungal penetration through the cuticle, and into the tick interior. Hyphae of ΔBbmsn2 , however, did not appear to penetrate or breach the tick exocuticle 120 h after treatment. Protease activity was lower on tick cuticles treated with ΔBbmsn2 than those treated with the wild-type or ΔBbmsn2/Bbmsn2 strains. These data show that loss of the Msn2 transcription factor reduced B. bassiana virulence against R. microplus , but did not interfere with conidial germination, appressoria formation or sporulation on tick cadavers, and plays only a minimal role once the cuticle is breached. Our results indicate that the BbMsn2 transcription factor acts mainly during the fungal penetration process and that decreased protease production may be one mechanism that contributes to the inability of the mutant strain to breach the tick cuticle. Competing Interests: ÉF is Associate Editor for the section Fungi-Animal Interactions in Frontiers in Fungal Biology, and Guest Associate Editor for the section Invertebrate Physiology, in the research topic: Entomopathogenic Fungi for the Control of Arthropods - Frontiers in Physiology. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. (Copyright © 2021 Muniz, Ribeiro-Silva, Arruda, Keyhani and Fernandes.)
Databáze:	MEDLINE
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