DUAL SECRETORY VESICLES CLUSTERING AND DYNAMICS DURING POLAR CELL ELONGATION IN THE PHYTOPATHOGENIC FUNGUS BOTRYTIS CINEREA

Filamentous fungi grow through a process of polar elongation that is supported by secretory vesicles. These vesicles provide lipids to extend the plasma membrane and, among others, enzymes to synthesize the cell wall. We used confocal microscopy to locate and analyze the dynamics of secretory vesicles transporting a fluorescent chitin synthase CHSIIIa in the plant pathogen Botrytis cinerea . Two populations of growing hyphae were identified, one exhibiting a typical spheroidal spitzenkörper at the apex, the other one with vesicles forming a crescent instead. Neither curvature of the apex nor hyphal width significantly differ between the two populations. Mean hyphal elongation was also no different between the two populations, with two co-existing patterns of pronounced and less pronounced stepwise extensions. In contrast the growing spitzenkörper-hyphae displayed repetitive fluctuations in fluorescence intensity at the apex that were not detected in the crescent-hyphae. Using Fast Fourier Transform, these fluctuations were found periodic, and a single oscillator was determined that could explain the experimental data.