Changes in Aspergillus nidulans gene expression induced by bafilomycin, a Streptomyces-produced antibiotic

In natural environments bacteria and filamentous fungi often compete for th e same resources. Consequently, production of antibiotic secondary metaboli tes and defence mechanisms against these compounds have evolved in these or ganisms. An experimental model has been developed to study the response in fungi exposed to one such antibiotic. The filamentous fungus Aspergillus ni dulans was treated with bafilomycin B-1, a Streptomyces-produced antibiotic which reduces radial growth rate and induces morphological changes in fung i. mRNA differential display was used to study changes in fungal gene expre ssion. For five genes, changes in abundance of the corresponding mRNAs, dir ectly or indirectly caused by bafilomycin, were observed. Of these, three w ere up-regulated and two repressed. With four of these the change in mRNA a bundance measured ranged from 10- to 60-fold. However, for one gene the mRN A was only detected after bafilomycin treatment. One of the downregulated m RNAs encodes ASPND1, a glycoprotein that belongs to a known family of antig ens identified in aspergilloma patients. One up-regulated mRNA shows sequen ce similarities, at the amino acid level, with a cell-wall protein of Sacch aromyces cerevisiae. The remaining three genes were also cloned and sequenc ed; their sequences do not correspond to known genes in A. nidulans, and no similarities with published nucleotide or protein sequences in other organ isms were found. These results indicate the feasibility of using mRNA diffe rential display to study interactions between bacteria and filamentous fung i.