Protective response mechanisms to heat stress in interaction with high CO2 conditions in Coffea spp.

Abstract

Modelingstudieshavepredictedthatcoffeecropwillbeendangeredbyfutureglobalwarming,butrecentreportshighlightedthathigh[CO2]canmitigateheatimpactsoncoffee.ThisworkaimedatidentifyingheatprotectivemechanismspromotedbyCO2inCoffeaarabica(cv.IcatuandIPR108)andCoffeacanephoracv.ConilonCL153.Plantsweregrownat25/20◦C(day/night),under380or700μLCO−2L1,andthengraduallysubmittedto31/25,37/30,and42/34◦C.Relevantheattoleranceupto37/30◦Cforboth[CO2]andallcoffeegenotypeswasobserved,likelysupportedbythemaintenanceorincreaseofthepoolsofseveralprotectivemolecules(neoxanthin,lutein,carotenes,a-tocopherol,HSP70,raffinose),activitiesofantioxidantenzymes,suchassuperoxidedismutase(SOD),ascorbateperoxidase(APX),glutathionereductase(GR),catalase(CAT),andtheupregulatedexpressionofsomegenes(ELIP,Chaperonin20).However,at42/34◦Catolerancethresholdwasreached,mostlyinthe380-plantsandIcatu.Adjustmentsinraffinose,lutein,b-carotene,a-tocopherolandHSP70pools,andtheupregulatedexpressionofgenesrelatedtoprotective(ELIPS,HSP70,Chape20,and60)andantioxidant(CAT,CuSOD2,APXCyt,APXChl)proteinswerelargelydrivenbytemperature.However,enhanced[CO2]maintainedhigheractivitiesofGR(Icatu)andCAT(IcatuandIPR108),kept(orevenincreased)theCu,Zn-SOD,APX,andCATactivities,andpromotedagreaterupregulationofthoseenzymegenes,aswellasthoserelatedtoHSP70,ELIPs,ChaperoninsinCL153,andIcatu.Thesechangeslikelyfavoredthemaintenanceofreactiveoxygenspecies(ROS)atcontrolledlevelsandcontributedtomitigateofphotosystemIIphotoinhibitionatthehighesttemperature.Overall,ourresultshighlightedtheimportantroleofenhanced[CO2]onthecoffeecropacclimationandsustainabilityunderpredictedfutureglobalwarmingscenarios