The Effect Of H~+-ATPase In PM Of Arabidopsis Thaliana Pollen Cells In Signal Transduction Pathway Of Extracellular CaM

There is currently an intense interesting in understanding the regulation of pollen germination and pollen tube growth. Active proton pump in plasma membrane(PM) of pollen grain drives H+ efflux, hyperpolarize the membrane potential and triggers signaling transduction. Extracellular calmodulin exerts multiple functions in plants, stimulates a cascade of intracellular signaling events to regulate the pollen germination and tube length. Extracellular calmodulin can activate hyperpolarisation-activated Ca²⁺-permeable channels, and generated spatio-temporal characteristic calcium signal. In this paper, pharmacological method and material in which reconstituted aequorin was transferred was applied to investigate the relationship between PM proton pump, calcium channel and extracellular calmodulin.We provide evidence that proton pump may stimulate pollen germination and tube length by activating PM calcium channel and lead elevation of cytosolic free calcium concentration. PM proton pump antagonist sodium vanadate may suppress exogenous calmodulin induced [Ca²⁺]cyt elevation, pollen germination and tube growth. These results suggest that extracellular CaM actives an intracellular signal pathway involving activation of proton pump and hyperpolarization-activated calcium channel.