Abstract:
Strain improvement of the insect pathogenic fungus Metarhizium anisopUae is necessary
to increase its virulence towards agricultural pests and thus improve its commercial
efficacy. Nevertheless, the release of genetically modified conidia in crop fields may
negatively affect the ecosystem. Controlling conidiation is a potential means of limiting
the release of engineered strains since conidia are the infective propagules and the means
of dispersal. The purpose of this study was to research the colony development of M.
anisopUae to identify potential targets for genetic manipulation to control conidiation.
Following Agrobacterium tumefaciem insertional mutagenesis, phenotypic mutants were
characterized using Y-shaped adaptor dependent extension PCR. Four of 1 8 colony
development recombinants had T-DNA flanking sequences with high homology to genes
encoding known signaling pathway proteins that regulate pathogenesis and/or asexual
development in filamentous fungi. Conidial density counts and insect bioassays
suggested that a Serine/Threonine protein kinase COTl homolog is not essential for
conidiation or virulence. Furthermore, a choline kinase homolog is important for
conidiation, but not virulence. Finally, the regulator of G protein signaling CAG8 and a
NADPH oxidase NoxA homolog are necessary for conidiation and virulence. These
genes are candidates for further investigation into the regulatory pathways controlling
conidiation to yield insight into promising gene targets for biocontrol strain improvement.
