From protoplasts to gene clusters

Advances in protoplast technology underpinned many crucial developments in our understanding of the molecular biology of filamentous fungi. This review follows one of these developments, namely the discovery and analysis of difuran toxin gene clusters. Our understanding of the biosynthetic pathway of the agriculturally important toxin, aflatoxin, has been dramatically enhanced by the use of protoplasts and protoplast-based gene transformation methods. Since the identification of the first pathway genes by complementation of mutants with transforming DNA, transformation has continued to play a critical role in the elucidation of gene function and regulation. But despite the wealth of knowledge accumulated so far some fundamental questions remain to be answered. How did these gene clusters evolve? What is the biological role of aflatoxin? The discovery of homologues of aflatoxin genes in other fungal species such as the pine needle pathogen Dothistroma septosporum may help to shed some light on these questions.