Elucidating three pathways that contribute to directional growth regulation in Candida albicans hyphae

The production of hyphae is strongly linked to pathogenesis during superficial mucosal infections and the life-threatening disseminated disease, invasive candidiasis. Hyphae constitute the ‘Special Weapons And Tactics’ capability deployed by C. albicans during mucosal and endothelial cell layer invasion. Hyphae are equipped with adhesins and secreted effectors but these are only effective if hyphal guidance mechanisms are operational to direct penetrative growth into host tissue. We have identified three distinct hyphal phenotypes in which the ability to respond normally to external cues is attenuated or lost. Each of the three phenotypes is produced by specific grouping of mutant or gene deletion strains. The functional links within some groupings are emerging. For example, a sinusoidal growth morphology is observed when Pxl1 or its putative kinase, Ptk2, are deleted. However, in other cases the relationship between the proteins in a grouping is less clear, demonstrating that there are significant gaps in our understanding of polarised growth in C. albicans. Our aim is to elucidate these signalling pathways and generate an integrated model of how hyphal guidance signals influence the molecular machinery that drives polarised growth.