Cdc42/Rho GTPases in fungi: variations on a common theme.

Cdc42/Rho GTPases are universally important regulators of cellular morphogenesis. Whereas their functions are well characterized in budding yeast, they are only beginning to be understood in filamentous fungi. The recent systematic analysis of Cdc42, Rac1 and Rho function in Aspergillus niger provides the first global perspective on their respective roles in hyphal morphogenesis. Surprisingly, the partitioning of these roles between Cdc42 and Rac1 seems to vary even among related fungi. These observations highlight the variable use of a common signalling module in filamentous fungi.