Pest Management Science (2020) 76, 758-768

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Haoyu Guo, Hongjuan Wang, Nemat O. Keyhani, Yuxian Xia and Guoxiong Peng (2020)
Disruption of an adenylate-forming reductase required for conidiation, increases virulence of the insect pathogenic fungus Metarhizium acridum by enhancing cuticle invasion
Pest Management Science 76 (2), 758-768
Abstract:
BACKGROUND
Metarhizium acridum, is a specific acridid pathogen developed for use against the migratory locust (Locusta migratoria manilensis). Adenylate-forming reductases (AFRs) include enzymes that are involved in natural product biosynthesis. Here, we genetically characterize the functions of a class IV AFR in M. acridum (MaAfr^IV) on fungal development and virulence.
RESULTS
Gene expression analyses indicated MaAfr^IV was induced on locust wings early during the infection process. Surprisingly, loss of MaAfr^IV increased virulence (25.20% decrease in the median lethal time) against the locust in topical bioassays but was no different than the wild type when the cuticle was bypassed by direct infection of conidia into the insect hemocoel. Virulence markers including protease (Pr1) expression and appressorial turgor pressure were higher in the mutant than the parent strain. No difference was seen in the expression of host immune genes (Toll pathway) or in polyphenol oxidase (PPO) activity in locusts infected by the ΔMaAfr^IV or wild type strains. However, the ΔMaAfr^IV strain was unable to successfully sporulate on dead cadavers.
CONCLUSION
Disruption of MaAfr^IV increased fungal virulence by promoting insect cuticle invasion without altering host immune response or fungal immune evasion. Although loss of MaAfr^IV conferred an apparent benefit to the fungus in terms of enhanced virulence, a significant trade-off was seen in the inability of the fungus to sporulate on the cadaver. As conidiation on the cadaver is essential for subsequent propagation in the environment, loss of MaAfr^IV can reduce the engineering strains survivability in the field and improve the safety.
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Link to article at publishers website

Database assignments for author(s): Nemat O. Keyhani, Yuxian Xia

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
molecular biology - genes
non-target effects/fate in environm.

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Locusta migratoria
Metarhizium acridum (entomopathogen)	Locusta migratoria