H+-ATPase in the plasma membrane of Arabidopsis pollen cells is involved in extracellular calmodulin-promoted pollen germination

In this paper, the role of the plasma membrane (PM) H+-ATPase in extracellular calmodulin (CaM)-promoted pollen germination and in tube growth of Arabidopsis thaliana was investigated. Pollen germination, pollen tube growth rate, free cytosolic Ca2+ concentration ([Ca2+]cyt) and Ca2+ channel activity in the PM of pollen cells were measured. In response to fusicoccin or CaM treatment, in vitro pollen germination and pollen tube growth rate, [Ca2+]cyt and activity of a hyperpolarization-activated Ca2+-permeable channel increased. Sodium vanadate inhibited the promotion of these parameters by extracellular CaM. The results suggest that H+-ATPase may be involved in extracellular CaM-regulated pollen germination and in tube growth by modulation of the hyperpolarization-activated Ca2+ channel in the PM of A. thaliana pollen cells.