Effect Of D-glucose On Stomatal Movement Of Arabidopsis Thaliana And Its Mechanism

D-glucose,as a signaling molecule,has important role in live of organism.D-glucose regulates various plant biological processes,including seed germination,seedling development,photosynthesis,nitrogen metabolism,stress response,flowering,senescence,death and so on.Although the role of D-glucose in plant growth and development has been adequately known,signal transduction pathway of D-glucose remains unclear.Stomata,control gas exchange and transpiration.Stomatal open and closure are regulated by several internal factors,such as abscisic acid,ethylene and SA,and external factors,including carbon dioxide,humidity,light,and pathogens.However,the effect of D-glucose on stomatal movement is not fully clear.D-glucose signalling pathway in the regulation of stomatal movement remains obscure.Here,we select Arabidopsis(Arabdopsis thaliana)wild-type and relevant mutants as plant material,through pharmacological and stomatal bioassay combined with fluorescent microscope method,to study the roles of regulator of G protein signaling protein(RGS protein),Ga protein,H2O2 and NO and the relationship between them in D-glucose-induced stomatal closure.The main results are as follows:1.D-glucose induced stomatal closure,its maximum biological response concentration and time are 125 mM and 2 h,respectively.Furthermore,the effect of D-glucose on stomata is metabolism-independent,hexokinase(HXK)-dependent,and irrelevant to osmotic stress.2.D-glucose closed stomata of the wild-type,but did not close stomata of RGS protein mutants rgsl-1 and rgsl-2 and Ga mutants gpal-3 and gpal-4,indicating that RGS protein and Ga protein are involved in D-glucose-induced stomatal closure.3.D-glucose induced H2O2 production in guard cells and stomatal closure in the wild-type,these effects were prevented by ASA and CAT,two H2O2 scavenger,and DPI,an inhibitor of NADPH oxidase.D-glucose induced H2O2 production in guard cells and stomatal closure in the wild-type and NADPH oxidase mutant AtrbohD,these effects were impaired in NADPH oxidase mutants AtrbohF and AtrbohD/F.The results show that AtrbohF-dependent H2O2 is required for stomatal closure by D-glucose.4.D-glucose induced NO production in guard cells and stomatal closure in the wild-type,these effects were prevented by c-PTIO,a NO scavenger and tungstate,an inhibitor of nitrate reductase.D-glucose induced NO production in guard cells and stomatal closure in the wild-type and nitrate reductase mutant Nia2-1,these effects were impaired in nitrate reductase mutant Nia1-2 and Nia2-5/Nia1-2.The data show that Nial-catalyzed NO mediats D-glucose-led stomatal closure.5.Exogenous H2O2 not only closed the stomata of rgsl-1 and rgsl-2,but also rescued the lesion of rgsl-1 and rgsl-2 in D-glucose-induced stomatal closure.These data indicate that RGS protein mediates D-glucose-triggered stomatal closure via regulating H2O2 production.This conclusion is supported by the fact that D-glucose induces H2O2 production in the wild-type,but does not in rgsl-1 and rgsl-2.6.Exogenous sodium nitroprusside(SNP)closed the stomata of rgsl-1 and rgsl-2,also restored the impairment of rgsl-1 and rgsl-2 in D-glucose-induced stomatal closure.The results show that RGS protein is involved in D-glucose-caused stomatal closure via inducing NO synthesis,which is further confirmed by the data that D-glucose induces NO synthesis in the wild-type,but does not in rgsl-1 and rgs1-2.In conclusion,RGS protein mediates D-glucose-stimulated stomatal closure via modulating AtrbohF-dependent H2O2 production and Nial-catalyzed NO accumulation.