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 phosphorylation motifs identified ill the glucose repressor from the phytopathogenic fungus Sclerotinia sclerotiorum were mutated in a GFP::CRE1 translational fusion. Complementation experiments in Aspergillus nidulans and fluorescence microscopy analyses showed that mutation of one site (Ser(266)) abolishes the repressor activity of the fusion protein but not its nuclear targeting, suggesting that an AMPK protein kinase may be involved in the function of the fungal glucose repressor.