The SWC4 subunit of the SWR1 chromatin remodeling complex is involved in varying virulence of Metarhizium brunneum isolates offering role of epigenetic regulation of pathogenicity

ABSTRACT

The host – pathogen interaction is a multifactorial process subject to a co-evolutionary arms race consisting of rapid changes in both host and pathogen, controlled at the genetic and epigenetic levels. Previously, we showed intra-species variation in disease progression and pathogenicity in aphids for Metarhizium brunneum isolates MbK and Mb7. Herein, we compared genomic, epigenetic, and metabolomic variations between these isolates and their effects on pathogenicity. Genomic variation could not completely explain the observed differences between the isolates. However, differential N6-adenine methylation (6 mA) and its correlation to reduced expression of the essential SWC4 subunit of SWR1 chromatin-remodelling complex (SWR1-C) led us to hypothesize a role for swc4 in the varying pathogenicity. Mutagenesis of the essential swc4 gene in MbKisolate resulted in reduction of secondary-metabolite (SM) secretion and impaired virulence in Galleria mellonella. Our results suggest the role of SWC4 in the regulation of SMs and the role of both SWC4 and SWR1-C in virulence of M. brunneum isolates. A better understanding of epigenetic regulation of SM production and secretion in entomopathogenic fungi may enable theirmanipulation for better biocontrol performance, and expand possibilities for environmentally friendly pest control.

KEYWORDS:

• Entomopathogenic fungi
• Galleria mellonella
• adenine methylation
• secondary metabolites
• Cas9-Mediated mutagenesis
• pathogenicity

Acknowledgement

We would like to thank Prof. Daniel Panaccione and Kyle Davis at West Virginia University for personal communications and assistance with the Cas9 protocol setup in Metarhizium brunneum. We acknowledge the contribution of Dr. Joshua Granek of Duke University for supporting the research conception. The work of D.M was supported by ARO Volcani Center Young Scientist Fund. The work of A.S. and F.V. was supported by a MISE CRESO grant no. Protection F/050421/01-03/X32; Viabio no. F/200095/01-03/X45; Regione Campania (Project Dioniso, no. B98H19005010009), and Regione Veneto (Project Divine).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/21505594.2022.2101210.

Additional information

Funding

The work was supported by MISE CRESO [F/050421/01-03/X32]; Viabio [F/200095/01-03/X45]; Regione Campania [B98H19005010009], and Regione Veneto.