Disruption of a major facilitator superfamily transporter responsible for acetic acid efflux, increases the virulence of the insect pathogenic fungus Metarhizium rileyi

Highlights

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    Deficiency of MrMFS1 was confirmed to underlie to the accelerated growth.
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    No morphological or physiological alterations were observed upon deletion of MrMFS1.
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    The deletion mutant exhibits enhanced stress tolerance and insecticidal activity.
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    MrMFS1 mediates the proton-coupled efflux of acetic acid.

Abstract

Identifying potential growth and virulence regulons that contribute to the efficacy of biopesticides has long been a central focus of biocontrol research. A short growth cycle and potent insecticidal activity represent critical selection criteria for both the discovery of novel fungal pesticides and the genetic improvement of existing ones. In this study, a mutant strain of Metarhizium rileyi with enhanced growth was generated via random T-DNA insertion. Sequence analysis revealed that the deficiency of MrMFS1—a membrane-embedded major facilitator superfamily (MFS) transporter coding gene—underlies the observed phenotypic alteration. Subsequently, a M. rileyi strain lacking the MrMFS1 gene was successfully generated by Agrobacterium-mediated transformation. Notably, this growth-promoting effect is consistently evident across diverse developmental stages and experimental conditions. In addition to displaying accelerated in vitro growth under various stress conditions, the mutant strain exhibited enhanced in vivo colonization of host insects, as evidenced by accelerated appressorium formation on the insect cuticle and rapid hyphal body development within the host’s intestinal tract. The MrMFS1 protein is a proton-coupled transporter responsible for the efflux of acetic acid. Disruption of the MrMFS1 gene leads to intracellular accumulation of this organic acid, which can serve as an endogenous carbon and energy source to promote fungal growth. This discovery provides valuable insights for re-evaluating the functional roles of MFS family members and lays a foundation for the future development of hypervirulent M. rileyi strains for microbial insect control.

Read full article for free (open access):
https://www.sciencedirect.com/science/article/pii/S2666517426000945



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