EATP Promotes Stomatal Opening Of Arabidopsis Thaliana Through Heterotrimeric G Protein α Subunit And PM H~+-ATPase

Stomata is the main path of gas absorption and water transpiration in plants. Eachstomata was surrounded by a pair of guard cells. Responding to changing enviroment, e.g.biotic or abiotic stress, guard cells adjust their osmotic pressure by regulate ion exchange.Stomata then open or close to modulate water balance in plants, which play a key role inmaintaining cell viability under stress.Heterotrimeric G protein participated signal cascades is significant in plant cells. Thesurvey of Arabidopsis genome only identifies a single canonical alpha gene, GPA1, of Gprotein α subunit. GPA1has been found to be involved in water metabolism regulation,especially in ABA regulated signaling in guard cells.The guard cell is the ideal system of verifying activity and signal transduction pathwayof H~+-ATPase in vivo. In guard cells, we can study H~+-ATPase and other regulatorycomponents related to water metabolism. H~+-ATPase has been revealed to be involved inABA, blue light and pathogen regulated stomatal movement.Based on our former results, heterotrimeric G protein α subunit (Gα) participates ineATP-induced stomatal opening,[Ca2~+]cytelevating, ROS generation and H~+efflux elevating.The physiological relevance and signal transduction of eATP in plant cells has been reported.As a signal molecule, eATP plays key roles in modulating vegetable and reproductive growth,responding to biotic or abiotic stimulation.In order to study the mechanism of eATP-induced stomatal opening, Arabidopsisthaliana was used as material, including wild type (ecotype ws and col-0),overexpressedlines of Gα(wGα、cGα),lost-of-function mutants of Gα (gpa1-1, gpa1-2) and H~+-ATPase(AHA1, AHA2, AHA5). The difference of stomatal movement responding to eATP treatmentbetween wild type and the mutants was investigated to verify the role of these signaltransducers in eATP regulated stomatal movement.The results showed that, in null mutants ofGα and AHA1, AHA2, AHA5, eATP-promoted stomatal opening, which was found in wildtype and overexpressed lines, was significantly impaired. Suggesting the involvement of Gαand some H~+-ATPase isoforms in signal transduction of eATP induced stomatal opening.Furthermore, to verify the role of various proton pump isoforms in eATP promoted H~+ efflux in guard cells, Scanning Ion-selective Electrode Technique (SIET) was used. Resultsshowed that, in guard cells of null mutants of AHA1, AHA2, AHA5, eATP promoted H~+efflux,which was detected in wild type, was strongly impaired. The results indicated that theseH~+-ATPase isoforms may be involved in eATP promoted H~+efflux, which will stimulatestomatal opening.