Functional analysis of dsRNAs (L1, L3, L5, and M2) associated with isometric 34-nm virions of Agaricus bisporus (white button mushroom)

cDNA clones of dsRNAs associated with La France disease of Agaricus bisporus were isolated, Clones corresponding to L1 and L5 dsRNAs were sequenced. The deduced amino acid sequence of L1 dsRNA (1078 amino acids, M(r) 121K) showed significant homology with RNA-dependent RNA polymerases of other dsRNA viruses. The deduced amino acid sequence of L5 dsRNA (724 amino acids, M(r) 82K) showed no homology with known proteins. Amino acid sequences of tryptic digests of three virion-associated proteins were determined. The 34-nm virion-associated protein of M(r) 115K was encoded by the L1 dsRNA, thus identifying this protein as the RNA-dependent RNA polymerase. The virion-associated protein of M(r) 90K was encoded by the previously sequenced L3 dsRNA. A cDNA clone of the previously sequenced M2 dsRNA was expressed in Escherichia coli and antibodies raised against this protein reacted only with a protein present in the cytoplasm of diseased A. bisporus fruit bodies but not in the 34-nm virions. (C) 1996 Academic Press, Inc

Ralstonia solanacearum lipopeptide induces chlamydospore development in fungi and facilitates bacterial entry into fungal tissues

Ralstonia solanacearum is a globally distributed soil-borne plant pathogenic bacterium, which shares a broad ecological range with many plant- and soil-associated fungi. We sought to determine if R. solanacearum chemical communication directs symbiotic development of polymicrobial consortia. R. solanacearum produced a diffusible metabolite that induced conserved morphological differentiation in 34 species of fungi across three diverse taxa (Ascomycetes, Basidiomycetes and Zygomycetes). Fungi exposed to this metabolite formed chlamydospores, survival structures with thickened cell walls. Some chlamydospores internally harbored R. solanacearum, indicating a newly described endofungal lifestyle for this important plant pathogen. Using imaging mass spectrometry and peptidogenomics, we identified an undescribed lipopeptide, ralsolamycin, produced by an R. solanacearum non-ribosomal peptide synthetase-polyketide synthase hybrid. Inactivation of the hybrid non-ribosomal peptide synthetase-polyketide synthase gene, rmyA, abolished ralsolamycin synthesis. R. solanacearum mutants lacking ralsolamycin no longer induced chlamydospore development in fungal coculture and invaded fungal hyphae less well than wild-type. We propose that ralsolamycin contributes to the invasion of fungal hyphae and that the formation of chlamydospores may provide not only a specific niche for bacterial colonization but also enhanced survival for the partnering fungus