Proteome analysis of Aspergillus nidulans reveals proteins associated with the response to the antibiotic concanamycin A, produced by Streptomyces species

Abstract.

Competition between microbes is common to all ecosystems, but the exact nature of the competition is in most cases unknown. We have previously studied the antagonism between Streptomyces halstedii and several fungi at both the organismal and gene expression levels. Here we analysed the effect of an antibiotic produced by Streptomyces, concanamycin A, on protein levels in the filamentous fungus Aspergillus nidulans. Two-dimensional gel electrophoresis revealed that 20 proteins either increased or decreased in abundance upon treatment of the fungus with the antibiotic. Five of the most prominent proteins which changed in abundance were identified based on peptide analysis by mass spectrometry. Two of these correspond to proteins previously described in A. nidulans, and three others are homologous to proteins found in other organisms. Of these, one down-regulated protein was identified as glyceraldehyde dehydrogenase, a protein involved in general metabolic pathways. A second down-regulated protein, CpcB, affects the initiation of sexual development. Among the proteins not previously described in A. nidulans, all of them up-regulated by concanamycin A, we found two proteins with described homologues in other fungal species. The first is homologous to a cadmium-induced protein in Candida sp. The second protein is homologous to LovC, an enoyl transferase involved in the biosynthesis of lovastatin, a secondary metabolite identified in A. terreus. A third protein has a homologue in A. niger, which is of unknown function. This study indicates that proteome analysis may be a useful method for studying effects on gene expression during competitive interactions between bacteria and filamentous fungi.