Genome‐wide identification of pathogenicity, conidiation and colony sectorization genes in Metarhizium robertsii

Abstract

Metarhizium robertsii occupies a wide array of ecological niches and has diverse lifestyle options (saprophyte, insect pathogen and plant symbiont), that renders it an unusually effective model for studying genetic mechanisms for fungal adaptation. Here over 20,000 M. robertsii T-DNA mutants were screened in order to elucidate genetic mechanism by which M. robertsii replicates and persists in diverse niches. About 287 conidiation, colony sectorization or pathogenicity loci, many of which have not been reported in other fungi were identified. By analysing a series of conidial pigmentation mutants, a new fungal pigmentation gene cluster, which contains Mr-Pks1, Mr-EthD and Mlac1 was identified. A conserved conidiation regulatory pathway containing Mr-BrlA, Mr-AbaA and Mr-WetA regulates expression of these pigmentation genes. During conidiation Mr-BlrA up-regulates Mr-AbaA, which in turn controls Mr-WetA. It was found that Hog1-MAPK regulates fungal conidiation by controlling the conidiation regulatory pathway, and that all three pigmentation genes exercise feedback regulation of conidiation. This work provided the foundation for deeper understanding of the genetic processes behind M. robertsii adaptive phenotypes, and advances our insights into conidiation and pigmentation in this fungus.

Unveiling the function and regulation control of the DUF3129 family proteins in fungal infection of hosts

“…B 374: 20180321 old PDA plates and applied topically by immersion of insects for 30 s in an aqueous suspension of 1 Â 10 7 conidia ml 21 . For the injection assay to bypass insect cuticles, an individual insect was injected from the second proleg with 10 ml of spore suspension (1 Â 10 6 conidia ml 21 ). Both topical and injection bioassays were also conducted to compare the virulence difference between WT and Mrst12 mutants using the 5th instar larvae of silkworm Bombyx mori.…”

“…The MAPK pathways have been well investigated in control of conidiation, pathogenicity and stress responses in Me. robertsii [19][20][21]. It is highly likely that the DUF3129 genes are the downstream effectors of MAPK pathway(s) and Ste12-like TF.…”

The Thm1 Zn(II)2Cys6 transcription factor contributes to heat, membrane integrity and virulence in the insect pathogenic fungus Beauveria bassiana

“…The recognition of white muscardine disease as the result of an infectious agent, and later, due to specific fungal pathogen, led to one of the first germ theories of disease (Ainsworth, 1956;Porter, 1973). Studies on these entomopathogenic fungi, typified by the members of the Metarhizium and Beauveria genera, are gradually being regarding as model systems applicable to uncovering fundamental aspects of fungal development, stress response and virulence, particularly as these fungi display shared and unique attributes in comparison to plant and animals pathogens (Lu and St Leger, 2016;Wang et al, 2016;Zeng et al, 2017). B. bassiana is both a broad host range insect pathogen and a plant mutualist (Boucias et al, 2018;Moonjely et al, 2018).…”

Alternative transcription start site selection in Mr-OPY2 controls lifestyle transitions in the fungus Metarhizium robertsii

“…They include an adhesin (MAD1) and hydrophobins that are responsible for adherence to the cuticle 12 , 13 , two chitin synthases for appressorial formation 14 , and a large number of cuticle-degrading enzymes for penetration of the cuticle 15 , 16 . Gene products associated with colonizing the hemocoel include the cold shock protein CRP1, laccase Mlac1, sterol carrier Mr-NPC2a, the collagen-like protein MCL1, enzymes for anaerobic respiration, and toxic secondary metabolites such as destruxins 17 – 22 . Major signaling pathway MAPK cascades and cAMP-PKA have been found to regulate both saprophytic growth and pathogenesis 23 , 24 .…”

“…Here, from analysis of a random T-DNA insertion library 22 , we identify a membrane anchor protein (Mr-OPY2) that controls the saprophyte-to-pathogen transition of M. robertsii . Mr-OPY2 protein levels are low during saprophytic growth, and when elevated they initiate appressorial formation.…”