A land plant specific VPS13 mediates polarized vesicle trafficking in germinating pollen

Surachat Tangpranomkorn, Motoko Igarashi, Fumiko Ishizuna, Yoshinobu Kato, Takamasa Suzuki, Sota Fujii, Seiji Takayama

ABSTRACT

Pollen has an extraordinary ability to convert from a dry state to an extremely rapidly growing state. During pollination, pollen receives water and Ca²⁺from the contacting pistil, which will be a directional cue for pollen tube germination. The subsequent rapid activation of directional vesicular transport must support the pollen tube growth, but the molecular mechanism leading to this process is largely unknown. Here we show that a plant-specific VPS13, AtVPS13a, mediates vesicle trafficking during the polarization process inArabidopsispollen.AtVPS13aknockout severely affected pollen germination and lipid droplet discharge, while Ca²⁺-dynamics after pollination was unchanged. Cellular distribution patterns of AtVPS13a and a secretory vesicle marker were synchronized, with a slight delay to the Ca²⁺-dynamics in polarizing pollen. The absence of AtVPS13a led to reduced cell wall deposition during pollen germination. These results suggest that AtVPS13a mediates pollen polarization, by regulating proper directional vesicular transport following Ca²⁺-signaling.