The TRP Ca2+ channel Yvc1 regulates hyphal reactive oxygen species gradient for maintenance of polarized growth in Candida albicans

Abstract

Candida albicans is an important opportunistic fungal pathogen, and hyphal polarized growth is critical for its invasive infection to the host. Both the vacuolar transient receptor potential (TRP) Ca²⁺ channel Yvc1 and the NADPH oxidase Fre8-governed reactive oxygen species (ROS) gradient are involved in hyphal development, but the relationship between Yvc1 and Fre8 during hyphal polarized growth remains to be investigated. Herein, we found that deletion of YVC1 led to dispersed distribution of ROS along the germ tube, while it was concentrated at the hyphal tip in WT cells. Moreover, Fre8 localization was altered as YVC1 was disrupted. Besides, similar to deletion of YVC1, addition of the Ca²⁺ chelating agent EGTA caused depolarization of Fre8-GFP in the wild-type cells, indicating the critical role of Yvc1-maintained Ca²⁺ gradient in polarized distribution of Fre8-GFP and consequent disruption of tip ROS gradient. By constructing a series of GFP-tagged polarized growth-related proteins, including Bud6, Exo70 and Lifeact, we found that these proteins, similar to Fre8 and ROS, had depolarized localization in yvc1Δ/Δ. Thus, our work provides a mechanic explanation of Yvc1-governed and ROS-related hyphal polarized growth, and shed a novel light on the role of Ca²⁺ signaling in maintenance of redox homeostasis and morphogenesis in the fungal pathogens.

Keywords: Candida albicans; Hyphal growth; Reactive oxygen species; Transient receptor potential Ca(2+) channel; Yvc1.