POLARIZED GROWTH OF FUNGAL HYPHAE IS DEFINED BY AN ALKALINE PH GRADIENT

Polarized cell growth is exhibited by a diverse range of eukaryotic an d prokaryotic cells. The events which are responsible for this growth are poorly understood. However, the existence of ion gradients may pla y an important role in establishing and driving cell polarity. Using a pH-sensitive, ratiometric fluorescent dye to monitor intracellular pH in growing fungal hyphae, we report a gradient at the extending hypha l tip that is up to 1.4 pH units more alkaline than more distal region s. Both the magnitude and the length of the pH gradient were strongly correlated with the rate of hyphal extension and eradication of the gr adient-arrested growth. These results suggest that alkaline pH gradien ts may be integral to hyphal extension in fungi. (C) 1996 Academic Pre ss.