The kinase cascade of the septation initiation network (SIN)/ mitotic exit network (MEN) plays a regulatory role for septation in fungi. The evolutionarily conserved MOB1 protein is a novel protein that is associated with the terminal kinase of this cascade. The exact role ofMOB1 is unclear. In the filamentous fungus A. nidulans, AnMOB1 is required for septation and conidiation, but is not essential for hyphal extension and colony formation. Because the A. nidulans mycelium contains multinucleate cells, novel mechanisms may exist to regulate septation in this organism. To identify novel septation regulators in A. nidulans, by UV mutagenesis we have isolated suppressor (smo) mutations that restored conidiation when AnMOB1 was down-regulated/not expressed. Microscopic examination indicated that the restored conidiation was concomitant with restored septation in the absence of the AnMOB1 protein. Among 110 independent smo mutants, five in two complementation groups demonstrated reduced hyphal growth, colony formation, and conidiation in the presence of AnMOB1. These five smo mutations also rendered hypersensitivity to low doses of the microtubule-depolymerizing agent benomyl. However, none of these smo mutations altered the localization of AnMOB1. Therefore, regulators antagonizing the SIN/MEN pathway likely exist in A. nidulans. Isolation of smo genes will shed light on regulatory mechanisms underlying septation in filamentous fungi. Progresses on characterization of the smo mutants, and identification of the smo genes will be presented. This work was supported by the NSF.
Full conference title:
23rd Fungal Genetics Conference
- Fungal Genetics Conference 23rd (2002)