Professor Hynes has made important contributions to eukaryotic gene regulation by studying catabolic pathways in filamentous fungi. Using classical and molecular genetics he was amongst the first to demonstrate multiple regulatory proteins controlling a single structural gene via a complex promoter. This work has also illuminated strategies used to coordinate carbon and nitrogen catabolism. His cloning of the Aspergillus nidulans amdS gene contributed significantly to the development of DNA mediated fungal transformation. His demonstration that this gene could be used to transform other fungal species has resulted in its widespread use in the genetic engineering of economically important fungi.