Mutation of a putative AMPK phosphorylation site abolishes the repressor activity but not the nuclear targeting of the fungal glucose regulator CRE1

In filamentous ascomycetes, glucose repression is mediated by CRE1, a zinc- finger protein related to Mig1p from yeast. Five putative AMPK phosphorylat ion motifs identified ill the glucose repressor from the phytopathogenic fu ngus Sclerotinia sclerotiorum were mutated in a GFP::CRE1 translational fus ion. Complementation experiments in Aspergillus nidulans and fluorescence m icroscopy analyses showed that mutation of one site (Ser(266)) abolishes th e repressor activity of the fusion protein but not its nuclear targeting, s uggesting that an AMPK protein kinase may be involved in the function of th e fungal glucose repressor.