Duplication of a Pks gene cluster and subsequent functional diversification facilitate environmental adaptation in Metarhizium species

Abstract

The ecological importance of the duplication and diversification of gene clusters that synthesize secondary metabolites in fungi remains poorly understood. Here, we demonstrated that the duplication and subsequent diversification of a gene cluster produced two polyketide synthase gene clusters in the cosmopolitan fungal genus Metarhizium. Diversification occurred in the promoter regions and the exon-intron structures of the two Pks paralogs (Pks1 and Pks2). These two Pks genes have distinct expression patterns, with Pks1 highly expressed during conidiation and Pks2 highly expressed during infection. Different upstream signaling pathways were found to regulate the two Pks genes. Pks1 is positively regulated by Hog1-MAPK, Slt2-MAPK and Mr-OPY2, while Pks2 is positively regulated by Fus3-MAPK and negatively regulated by Mr-OPY2. Pks1 and Pks2 have been subjected to positive selection and synthesize different secondary metabolites. PKS1 is involved in synthesis of an anthraquinone derivative, and contributes to conidial pigmentation, which plays an important role in fungal tolerance to UV radiation and extreme temperatures. Disruption of the Pks2 gene delayed formation of infectious structures and increased the time taken to kill insects, indicating that Pks2 contributes to pathogenesis. Thus, the duplication of a Pks gene cluster and its subsequent functional diversification has increased the adaptive flexibility of Metarhizium species.

Horizontal gene transfer allowed the emergence of broad host range entomopathogens

“…They are essential for infectivity to insects, suggesting that their acquisition and retention contributed to the emergence of entomopathogenicity in Metarhizium. Entomopathogenicity is advantageous, as it enables Metarhizium to escape competition from other microbes and build up population levels greater than the carrying capacity of the rhizosphere (31). Heterologous expression of the HGT protease (MAA_01413) upregulated expression of M. acridum's native cuticle-degrading enzymes on nonhost cuticle.…”

A M35 family metalloprotease is required for fungal virulence against insects by inactivating host prophenoloxidases and beyond

“…For complementation of MrM35-4 gene deletion, the full-length MrM35-4 gene including the promoter and 3ʹ-UTR region was amplified and cloned into the binary vector pDHt-Ben (conferring benomyl resistance) and the obtained plasmid was used to transform the null mutant ΔMrM35-4 for gene rescue. For overexpression of MrM35-4, the gene was made under the control of the constitutive Tef-gene promoter [35] and the P tef ::MrM35-4 fusion cassette was cloned into the plasmid pDHt-Ben to transform the WT strain of M. robertsii to obtain the mutant WT::OE. The drug resistance mutants were verified by PCR with different primers (Table S1).…”

RPW8/HR Repeats Predict NLR-dependent Hybrid Performance

“…The emergence of new variants is favored by many NLR genes being organized in tandem clusters, which can spawn new alleles as well as copy number variation by illegitimate recombination, and by the presence of leucine rich repeats in NLR genes, which can lead to expansion and contraction of coding sequences [31][32][33]. Cluster expansion has been linked to diversification and adaptation in a range of systems [34][35][36]. Several complex plant NLR loci provide excellent examples of cluster rearrangement increasing pathogen recognition specificities [29].…”