The Primary Investigation Of The Effect And Signal Transduction Of Extracellular ATP In Pollen Germination Of Arabidopsis Thaliana

Pollen germination and pollen tube growth is one of the model systems of cell signal transduction and polar growth.[Ca²⁺]_cyt plays an important role in pollen germination and pollen tube growth.Both heterotrimeric G protein and calcium channel on plasma membrane (PM) can regulate pollen germination and tube growth through regulating[Ca²⁺]_cyt and Ca²⁺ signaling.As a signaling agent,extracellular ATP(eATP) plays a significant role in plant growth and development,as well as resistance response.In this paper,we investigated the effect and mechanism of exogenous ATP on pollen germination of Arabidopsis thaliana. Electro-physiological technique was applied to detect the role of eATP on calcium channel in plasma membrane of Arabidopsis pollen cell.We also studied whether heterotrimeric G protein was involved in the regulative pathway of eATP on pollen germination using various mutants of G protein.Our results suggest that exogenous ATP leads to an obvious decrease of pollen germination percentage in a dose-dependent manner.Along with the increasing of eATP concentration,pollen germination percentage became lower and lower.Exogenous ADP can also induce an effective decrease of pollen germination.But AMP and adenosine show no remarkable effect on pollen germination.By using whole-cell patch clamping,a hyperpolarization-activated Ca²⁺ channel was recorded in plasma membrane of pollen grain.Exogenous ATP remarkably inhibited the calcium channel activity,suggesting that eATP-induced decrease of pollen germination may result from the inhibition of eATP on calcium channel in PM and the consequent decrease of calcium influx.Exogenous ATP decreased the germination percentage of all G-protein mutants and the wild type similarly,and so as to the ca²⁺ currents,indicating that G protein may be exclusive from the pathway of eATP-inhibited pollen germination and calcium channel activity.