Our primary interest is how cells spatially and temporally regulate their growth. Polarized growth is essential for both internal organization of cells and generation of complex multi-cellular structures. Oriented cell growth requires the specification of a site for polarized growth, orientation of the cytoskeleton towards this site, and subsequent directed growth.

Our goal is to understand the mechanisms of polarized growth, cell morphogenesis, and development in yeast. The yeast Saccharomyces cerevisiae reproduces during its haploid mitotic life cycle by a form of cell division termed budding. When haploid cells of the opposite mating type come in contact they direct their growth towards their mating partner forming pear shaped polarized cells called shmoos. These two polarized cells grow towards one another and following contact fuse to form diploid zygotes. Upon nitrogen starvation diploid yeast cells switch growth from unicellular budding to filamentous form comprised of chains of elongated cells called pseudohyphae. The human pathogenic yeast Candida albicans switches from an oval yeast form to a hyphal form and these hyphal filaments can invade into solid surfaces. This dimorphic switch is critical for pathogenicity of this commensal.

 
In these three growth processes asymmetric cell growth is accomplished by polarization of the actin cytoskeleton and subsequent localized growth by directed membrane traffic. During budding, polarized growth is initiated by internal signals whereas during mating and hyphae formation, polarized growth is dictated by external signals. We are interested in how internal and external signals are linked to directional growth. We are examining the roles of small G-proteins and phosphoinositide lipids in S. cerevisiae and C. albicans polarized growth. Furthermore we are investigating the role of all protein kinases and phosphatases in C. albicans filamentous growth and biofilm formation.