Abstract 1677 Investigating the role of HGC1 in hyphal development and maintenance using auxin-inducible degrataion in Candida albicans

Candida albicans is a fungal species found in the gastrointestinal tract and mucosal membranes.It is usually harmless but can become an opportunistic pathogen in people who are immune-compromised.In rare cases, it can cause invasive candidiasis, when the fungus spreads to internal organs such as the liver and kidneys, often disseminating through the bloodstream.The mortality rate of invasive candidiasis is 10-50% depending on many internal and external factors.C. albicans has two morphological states: the yeast state and the filamentous state.Both are required for pathogenesis.Hgc1 is an essential protein for promoting the hyphal state.Hgc1 is only expressed in hyphae and forms a complex with cyclin-dependent kinase (Cdk1) to phosphorylate target proteins that promote hyperpolarized growth and suppress cell separation.However only a few protein substrates of Hgc1-Cdk have been identified.Since hyphal growth in C. albicans is required for virulence, substrates regulated by Hgc1 might be useful targets for antifungal drugs.The objective of this project is to identify Hgc1-Cdk substrates to better understand how it promotes and maintains the hyphal state.To characterize Hgc1 function in hyphal maintenance, we need a tool to disrupt it after hyphae have started to develop, and we chose the auxin-inducible degradation (AID) system for this.The AID system is used to rapidly degrade a target protein of interest to observe the resulting phenotypic effects.Target degradation is activated by adding the plant hormone auxin to the culture media.My immediate objective has been to test if auxin-induced Hgc1 degradation is sufficient to phenocopy the hyphal defects of hgc1 deletion strains and if hyphal growth is rapidly arrested upon auxin addition.If so, then AID can be used to study the mechanisms by which Hgc1 maintains polarized hyphal growth and prevents cell separation.I am testing suitability of the AID system by inducing hyphal growth and then adding auxin to our HGC1-AID strain and observing the effects by light microscopy at different time points.I am comparing the length and number of hyphal cells over time with and without auxin.The expected result is that auxin treatment will cause hyphal elongation to stop, and cell separation to begin.