Regulation of septum formation by the SIN, MOR and BUD modules

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Fungi are outstanding models for the analysis of fundamental mechanisms underlying growth and differentiation. They represent the second largest group of eukaryotic organisms on earth and are recognized for their importance in ecology, biotechnology and their role as plant and human pathogens. Most fungi form mycelial colonies that consist of networks of branched hyphae, grow by apical extension and are compartmentalized by perforated cross-walls, called septa. This segmentation of communicating cell units is the basis for the morphological complexity achieved by the fungi and for the success of the fungal kingdom. Despite the importance of septation for fungal growth, proliferation and differentiation, our understanding of septum formation and its regulation is highly fragmentary. Based on our preliminary and published data on the interplay between two NDR kinase cascades and the BUD3-BUD4 landmark complex, we will determine (i) the composition and regulation of the septation initiation network, (ii) its potential connection with microtubule organization and nuclear behavior, (iii) the actin dynamics during septum placement and formation of the contractile actmyosin ring, (iv) the cross-regulation of the SIN/MOR networks, and (v) characterize candidate targets of the SIN/MOR kinases during septation initiation and termination. Using classical and molecular genetic approaches along with kinase and Rho GTPase biochemistry and life-microscopy we will dissect the mechanisms that control septation in a model mold. This project will provide insight into the fundamental mechanisms controlling growth and differentiation of multinucleated eukaryotic cells.