The Role And Relationship Of OST1, GHR1, GORK And SLAC1 In Ethylene-induced Stomatal Closure

Ethylene,as an endogenous plant hormone,regulates many aspects of plant growth and development and mediates the response of plant to abiotic and biotic stress.A previous study has shown that AtrbohF-dependent H2O2 production and Nial-catalyzed NO synthesis are essential for ethylene-induced stomatal closure.NO has also been confirmed to act downstream of H2O2 during ethylene-induced stomatal closure in Arabidopsis thaliana.Open Stomata 1(OST1),Guard Cell Hydrogen Peroxide-resistant 1(GHR1),Guard Cell Outward-rectifying K+ Channel(GORK),Slow Anion Channel-associated 1(SLAC1),H2O2 and NO have been known to mediate ABA-induced stomatal closure.However,whether OST1,GHR1,GORK and SLAC1 are involved in ethylene-induced stomatal closure remains unknown.Here,we used Arabidopsis(Arabidopsis thaliana)wild-type and relevant mutants,and studied the roles of OST1?GHR1,GORK and SLAC1,and the relationship between them and H2O2 and NO during ethylene-led stomatal closure by means of stomatal bioassay,fluorescent microscope and Reverse Transcription PCR(RT-PCR)technology.The main results were as follows:1.ACC,an immediate precursor of ethylene,closed the stomata of the wild-type,but did not close the stomata of OST1 mutants ost1-3 and ost1-4,GHR1 mutant ghr1,ost1ghr1,GORK mutant gork and SLAC1 mutants slac1-1,slac1-3 and slac1-4.The results indicate that OST1,GHR1,GORK and SLAC1 are involved in ethylene-induced stomatal closure.2.Unlike ostl mutant,which reduced ACC-induced H2O2 generation,ghr1 mutant did not affect H2O2 production in guard cells.Both ostl and ghr1 impaired ACC-induced NO synthesis.H2O2 closed the stomata of the wild-type and ost1,but did not close those of ghr1.However,sodium nitroprusside(SNP),a NO donor,closed the stomata of the wild-type,ost1 and ghr1.The data indicate that OST1 regulates H2O2 production,whereas GHR1 mediates H2O2-induced NO synthesis in guard cells.3.ACC triggered H2O2 and NO production in guard cells of the wild-type,gork and slac1,H2O2 and SNP closed the stomata of the wild-type,but did not close those of gork and slac1.The data support that H2O2 and NO mediate ethylene-led stomatal closure via regulating GORK and SLAC1.4.ACC induced GORK and SLAC1 genes expression in the wild-type leaves,these effects were reduced in AtrbohF and Nial-2.ACC increased NIA1 expression in the wild-type leaves,the effect was impaired in ghrl and AtrbohF.ACC stimulated RBOHF expression in the wild-type and ghr1 leaves,this effect was attenuated in ost1-3.Additionally,ACC-induced GHR1 expression in the wild-type leaves was slightly inhibited in ost1-3.The data show that OST1 triggers AtrbohF-dependent H2O2 production,then induces Nial-catalyzed NO synthesis via GHR1,and finally regulates GORK and SLAC1 function.Together,our results strongly suggest a signaling pathway in which ethylene induces OST1 expression,thereby stimulating AtrbohF-dependent H2O2 production,and then promotes Nial-catalyzed NO synthesis via GHR1,and finally closes stomata via regulating GORK and SLAC1 function in Arabidopsis.