Cdc42 GTPase dynamics control directional growth responses

Abstract

Significance The growth of many cell types combines polarized elongation with directional responses to external cues. We have previously linked Ca 2+ influx with directional growth in fungi and show here that Ca 2+ influx can rescue phenotypes caused by genetic disruption of two Cdc42 GTPase plasma-membrane trafficking pathways that are required for polarity establishment, hence restoring directional polarization. Constitutive activation of Cdc42 reversed the direction of polarization, which was also enhanced by the provision of exogenous Ca 2+ . Our model proposes that Ca 2+ transport amplifies weak directional growth signals specified by activated Cdc42 by promoting Cdc42 trafficking to the plasma membrane, thereby enhancing its directional regulation of polarized growth.

Pulses of Ca 2+ coordinate actin assembly and exocytosis for stepwise cell extension

“…Although the time needed for assembly of polarity markers may be one reason for oscillatory growth, it may also be a mechanism for the cells to respond more quickly to both internal and environmental cues, including chemical and mechanical stimuli. Indeed, Ca 2+ influx by the Ca 2+ channel Cch1 in Candida albicans is involved in the control of directional growth of hyphae (43). The stepwise growth coordinated by transient Ca 2+ influx could link growth with chemotropism and chemotaxis.…”

New “haploid biofilm model” unravels IRA2 as a novel regulator of Candida albicans biofilm formation

“…In C. albicans , small GTPases such as Cdc42 and Ras1 have been extensively investigated for their roles in regulating hyphal growth and tissue invasion111220212223. To unravel novel gene functions, we have constructed a haploid gene-deletion library covering mostly genes encoding uncharacterized GTPases and their regulators listed in the Candida Genome database (manuscript in preparation).…”

Endocytosis and exocytosis in hyphal growth

“…Fungi are able to rearrange their growth axes in response to environmental cues (Brand et al, 2014;Hoch et al, 1987;Stephenson et al, 2014), and this involves a rapid dissolution and reorganization of the endocytic and exocytic machinery. How these processes become polarized and coupled, however, is unclear.…”