Aspects on evolution of fungal β-lactam biosynthesis gene clusters and recruitment of trans-acting factors

The evolutionary origin of ß-lactam biosynthesis genes has been the subject of discussion for many years, and two main hypotheses have been proposed: (i) horizontal gene transfer (HGT) from bacteria to fungi or (ii) vertical decent. Recently obtained data reviewed here, strongly support the model of a combination of interkingdom HGT and recruitment of a biosynthesis gene and its cis-acting sites upon gene duplication.