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Disruption of an adenylate‐forming reductase required for conidiation, increases virulence of the insect pathogenic fungus Metarhizium acridum by enhancing cuticle invasion
Author(s) -
Guo Haoyu,
Wang Hongjuan,
Keyhani Nemat O,
Xia Yuxian,
Peng Guoxiong
Publication year - 2020
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.5576
Subject(s) - biology , conidiation , virulence , microbiology and biotechnology , migratory locust , metarhizium , entomopathogenic fungus , locust , pathogenic fungus , pathogen , metarhizium anisopliae , conidium , fungus , botany , gene , beauveria bassiana , biological pest control , genetics
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 Δ MaAfr IV or wild type strains. However, the Δ MaAfr 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. © 2019 Society of Chemical Industry