Figure 5.

Comparative genomic analysis of gene families that function in polarized filamentous growth in the Fungi. (a) Cartoon outlining proteins and complexes involved in polarized growth in Saccharomyces cerevisiae (this is a variation of a figure shown in [80]). Vesicles are delivered from the Golgi (a(i)) along cytoskeleton tracks to predetermined sites on the plasma membrane. Cdc42p is activated by Cdc24p (a(ii)) promoting [84] assembly of the polarisome complex (a(iii)) resulting in the formin Bni1p radiating actin cables [85,86]. Msb3p and Msb4p interact with Spa2 in the polarisome (a(iv)) which is thought to recruit Cdc42 from the cytosol at the site of tip growth [87]. Post-Golgi secretory vesicles are transported along actin cables using a type V myosin motor protein [88,89] (a(v)), to dock with the exocyst complex in a process dependent on Sec4 and its GEF Sec2 [90,91] (a(vi)) and so the vesicle is guided to its target site on the plasma membrane [92]. Cdc42p and Rho1 are required for localization of Sec3p, which together form a spatial marker for the exocyst (a(vii)) and Rho3p and Cdc42p mediate vesicle docking (a(viii)). Cdc42p plays a key role in regulating these processes in S. cerevisiae but in Pezizomycotina and basidiomycete fungi equivalent functions are performed by Rac1p [93,94]. (b) The domain architecture of the 17 proteins associated with polarized growth in fungi. (c) The taxon distribution of putative homologues of polarized growth proteins across a representative set of taxa including the Pseudofungi. ‘P’ indicates a putative paralogue relationship as identified using phylogenetic analysis.