We have been focusing on the yeast to hyphal transition, as well as subsequent filamentous growth,
both that of the main filament apex and filament branching, in the human fungal pathogen,
Candida albicans. Filament branching results in an increase in the number of growth sites and may
play a role in virulence in this fungal pathogen [1,2]. We have been using live-cell microscopy to
investigate these processes in C. albicans and to analyze morphological, as well as molecular,
changes associated with these transitions. Our results indicate that filament branching is a distinct
growth state. Specifically, we observe differences between branch and main filament growth,
together with distinct distributions and/or levels of reporters for exocytosis, endocytosis and
critical lipids. In contrast, the distribution and level of the key polarity small GTPase Cdc42 are
similar between branch and main filament growth. We have also been investigating the biophysical
characteristics of the cytoplasm using a micro-rheological probe [3], and observed a striking
difference between these growth processes with respect to cytoplasmic crowding, as well as in
response to antifungal drugs. In summary, at the cellular scale, our results reveal that filament
branching is a distinct growth process. Furthermore, at the sub-cellular scale, our results reveal
differences in the cytoplasm during morphogenesis and response to antifungal drugs.

[1] Barelle CJ et al. Eukaryot. Cell 2003 2:398-410.
[2] Veses V et al. Mol Microbiol. 2009 71:505-19.
[3] Delarue M et al. Cell 2018 174:338-49.