An F-Box/WD40 repeat-containing protein important for Dictyostelium cell-type proportioning, slug behaviour, and culmination

FbxA is a novel member of a family of proteins that contain an F-box and WD 40 repeats and that target specific proteins for degradation via proteasome s. In fruiting bodies formed from cells where the fbxA gene is disrupted (f bxA(-) cells), the spore mass fails to fully ascend the stalk. In addition, fbxA(-) slugs continue to migrate under environmental conditions where the parental strain immediately forms fruiting bodies. Consistent with this la tter behaviour, the development of fbxA(-) cells is hypersensitive to ammon ia, the signaling molecule that regulates the transition from the slug stag e to terminal differentiation. The slug comprises an anterior prestalk regi on and a posterior prespore region and the fbxA mRNA is highly enriched in the prestalk cells. The prestalk zone of the slug is further subdivided int o an anterior pstA region and a posterior pstO region. In fbxA(-) slugs the pstO region is reduced in size and the prespore region is proportionately expanded. Our results indicate that FbxA is part of a regulatory pathway th at controls cell fate decisions and spatial patterning via regulated protei n degradation. (C) 2000 Academic Press.