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• Yeast-like cells from solid and liquid media have similar virulence. • Yeast-like cells of Metarhizium rileyi express specific genes related to virulence. • Yeast-like cells grown on solid medium express unique genes. • Few up-regulated orthologous genes in common between M. rileyi and M. anisopliae yeast-like cells. • Many unknown protein-coding genes up-regulated in the yeast-like cells from solid medium. Metarhizium rileyi is an entomopathogenic fungus with a narrow host range which distinguishes it from other Metarhizium species with broad host ranges. This species is also unique because the initial yeast-like growth on solid media is only observed in liquid culture in other Metharizium species. A lack of knowledge about the metabolism and genetic signatures of M. rileyi during this yeast-like phase on solid and in liquid media is a bottleneck for its large-scale production as a commercial biocontrol agent. In this study we found that M. rileyi yeast-like cells produced on solid medium infected and killed the important insect pest Spodoptera frugiperda with comparable efficiency as yeast-like cells grown in liquid medium. Secondly, we used comparative transcriptomic analysis to investigate the active genes and genomic signatures of the M. rileyi yeast-like morphotypes produced on solid and in liquid media. Yeast-like cells grown in liquid medium had upregulated genes relating specifically to signal transduction and particular membrane transporters. Thirdly, we compared the transcriptomic profiles of yeast-like phases of M. rileyi with those of M. anisopliae. The yeast-like phase of M. rileyi grown on solid medium upregulated unique genes not found in other Metarhizium species including specific membrane proteins and several virulence factors. Orthologous genes associated with heat shock protein, iron permease, membrane proteins and key virulence traits (e.g. collagen-like protein Mcl1) were upregulated in both species. Comparative transcriptome analyses of gene expression showed more differences than similarities between M. anisopliae and M. rileyi yeast-like cells. [ABSTRACT FROM AUTHOR]

Abstract: The discovery of novel secretome proteins can add to our understanding of host–pathogen interactions. Here we report a rich diversity of secreted proteins from the interaction between grain aphids (host, insect order Hemiptera) and fungi of the order Entomophthorales (insect pathogens). The proteins were identified using a unique method unbiased by known sequences or functions to screen a cDNA library constructed directly from field-sampled material. We show for the first time that fungi from the genera Pandora and Entomophthora are armed with a battery of hydrolytic enzymes for penetrating the host cuticle. This enables both access to the hemolymph and exit for sporulation. Further, they secrete enzymes, most notably a number of lipases, for digestion of easily accessible high-energy compounds in the hemolymph. In contrast, we identified only few host genes potentially involved in the interaction, indicating that aphids respond only weakly to the pathogens. These results support recent findings that aphids have a reduced immune repertoire. [Copyright &y& Elsevier]