第16章应激生理学

PlantsStressResponsesandtheUnderlyingMechanismsAdverseenvironmentalfactorstoplants,suchasdrought,water-logging,salinity,highorlowtemperatures,airpollutes,highlight(visibleorUVlights),heavymetals,infection,grazingandetal.1.Whatisstress?IntroductionStressBioticStressAbioticStressDiseasesHerbivoryWeedsInsectsWaterTemperatureLightNutritionSalineHeavymetalsOxygenRadiation…..2.Whystudystressphysiologyofplants?

DroughtasanexamplePlantsaresessileandthereforecannotescapefromabioticstressfactors.StressTolerancePLANTPhysiologyandMolecularBiologyPlantBreedingandGeneticEngineeringTheincidenceofmajordroughtsisontheriseChinaexperiencedamajordroughtin2011ExtremeSevereModerateRed=decreasedplantproductivityGreen=increasedMajordroughtsandheatwavesinChina,RussiaandAustraliahaveimpactedfoodproductionandraisedpricesRussiaexperiencedheatwaves,droughtandwildfiresin2010Imagecredit:UnitedNationsEconomicCommissionforAfrica,2008AfricaReviewReportonDroughtandDesertificationChristopherColumbusRe-discoveringofAfricaIn2011seedcompaniesreleasedwater-optimizedcornBothofthesevarietiesweredevelopedusingmodernmolecularbreedingmethodswithouttheuseofrecombinantDNA3.Plants’strategiestocopewithstressStressescapeStressavoidanceStresstoleranceandstressresistanceTheyareoftenusedinterchangeablyinliteratures“Stresstolerance”ispreferableHowever,theymighthavesubtledifference:tolerance:passivemechanismsresistance:activemechanismsAvoidanceTolerance/ResistanceTolerance/ResistanceStressavoidanceStresstolerance猴面包树肉苁蓉4.StressresponsesAdaptation:geneticallydeterminedleveloftolerance/resistanceacquiredbyaprocessofselectionovermanygenerationsAcclimation:increaseofstresstolerancebypre-exposingtostressorhardeningStressresponsesatvariouslevelsAnatomicalandmorphologicallevelusuallyavoidanceCellularlevelBiochemicallevelMolecularlevelSecondarystresses:stressesresultingfromaprimarilyimposedstressfactorWaterdeficitmayleadtoheatstressinleavesFreezingstressleadstowaterdeficitandosmoticstressOxidativestressisalwaysinducedbyotherstressesCross-tolerance:tolerancetoonestressinducedbyacclimationtoanother.impliesthatmechanismsoftolerancetoseveralstressessharemanycommonfeaturesCross-toleranceexample:chillingstress-inducedgenesinvolvedinmultiplestressesMembranesystemsarethemajortargetsofmostabioticstressesBoundaryLayerofcellsandorganellesMetaboliccompartmentationsElectrontransportSignalperceptionATPgenerationSolutetransportIonpumpsIonchannelsCarrierproteinsElectricalexcitabilityAnchoringpointsforproteinsCommonresponsesofplanttovariousstressesMembranelipidsThylakoidmembraneERmembranePlasmamembraneMonogalactosyldiglyceride4212Digalactosyldiglyceride3323Sulfolipide500Phosphatidylcholine54519Phosphatidylethanolamine11517Phosphatidylserine013Phosphatidylglycerol11612Phosphatidylinositol082Sphingolipids0107Sterols0531Thecompositionofmembranelipidsinvariousorganellemembranes.甘油酯LeavesfromRye,afterLochnitetal.(2001)Thefluidityofthemembraneisgovernedbytheproportionofunsaturatedfattyacidsandthecontentofsterols.FattyacidChainlength:doublebondsMeltingpointLauricacid12:040°CStearicacid18:070°COleicacid18:113°CLinoleicacid18:2-5°CLinolenicacid18:3-11°CHydrophilicconstituentsofmembranelipids:phosphateandphosphateesters.Hydrophilicconstituentsofmembranelipids:hexoses.Hydrophilicconstituentsofmembranelipids:sphingolipids.FattyacidcompositionofmitochondriaisolatedfromWT,fad2andFAD3+cellsculturedat22oCorsubmittedto9oCfor3d.PlantCellPhysiol,2007,48,856-865Stressesaltermembranefluidity.LipidandfattyacidcompositionsPlantPhysiol,2006,141,1012-1020Stressesincreaseplasma-membranepermeability.Ion/electrolyteleakageisusedwidelyasanindexforstresstoleranceOxidativestressasasecondarystress

ReactiveOxygenSpecies(ROS)orActiveOxygenspecies(AOS):HydrogenperoxideSuperoxideanionHydroxideradicalLipidperoxidesSingletoxygenNitricoxideandnitrogenoxidesOtheroxygen-containingradicals

PlantPhysiol,2009,151,755-767Cold,nitricoxideBiolChem,2002,277,559-565pathogen,H2O2PNAS2004,101,8827-8832k+deprivation,H2O2StressesinduceROSproduction.ROSgenerationinchloroplast:pseudocyclicelectrontransport.O2

PSII

PQ

Cytb6/f

PC

PSIFdO2Hydrogenperoxideproducedbypseudocyclicphosphorylation(Mehlerreaction)inchloroplasts,electrontransportinmitochondria,photorespirationinperoxisomes,andspecificenzymessuchasNADPHoxidase,actsasasignalingmolecule.Theoxidantsignalistransducedinthenucleusprimarilyfortranscriptionandinthemitochondriontoinitiateprogrammedcelldeath.AnnuRevPlantBiol,2005,56,187-220Hydrogenperoxidegenerationinaphotosyntheticplantcell.Causinginjuries:Theymustberemovedactivelybyantioxidativesystem:Enzymes:SOD,POD,CAT,GRLowmolecularweightantioxidants:GSH,ascorbicacid,cysteine,carotenoids,xanthin,phenolcompounds,etal.Servingassignals:SecondmessengersRedoxsignaling:ROS/AOSaretwo-edgedswords.Schematicrepresentationofthesubcellularhydrogenperoxide(H2O2)metabolismanditsgenerationbythepathwayofphotorespirationandsubsequentsignalingthroughtheglutathionepoollinkedtotheascorbate-glutathionecycle,aswelltheproductionofascorbateinthemitochondriaanditssubsequenttransporttotheapoplast,whereitisoxidizedbyapoplasticenzymesrelatedtoextracellularredoxsignalingpathways.AO,ascorbateperoxidase;AGC,ascorbate‐glutathionecycle;APX,ascorbateperoxidase;CAT,catalase;DH,dehydrogenases,DHA,dehydroascorbate;DHAR,DHAreductase,GO,glycolateoxidase,GR,glutathionereductase;MDHA,monodehydroascorbate;MDHAR,MDHAreductase;OX,oxidases;PET,photosyntheticelectrontransferchain;Pi,inorganicphosphate;POX,peroxidase;RET,respiratoryelectrontransferchain;RuBisCO,ribulose‐1,5‐bisphophatecarboxylaseoxygenase.Munné-Bosch,Setal.Theimpactofglobalchangefactorsonredoxsignalingunderpinningstresstolerance.PlantPhysiol,2012Schematicrepresentationoftheintracellularandextracellularredoxsignalingnetworksinvolvinghydrogenperoxide(H2O2)andsingletoxygen(1O2)generatedbychloroplastsandextracellularapoplasticprocessesandozone(O3).β‐COP,β‐caroteneoxidationproducts;DHA,dehydroascorbate;MAPK,mitogen‐activatedproteinkinase;MDHA,monodehydroascorbate;MDHAR,MDHAreductase;HO•,hydroxylradical;PQ,oxidizedplastoquinone;PQH2,reducedplastoquinone;POX,peroxidases;PSI,photosystemI;PSII,photosystemII;RLK,receptorlikekinase;O2•‐,superoxide;SOD,superoxidedismutase.Munné-Bosch,Setal.Theimpactofglobalchangefactorsonredoxsignalingunderpinningstresstolerance.PlantPhysiol,2012ROS/redoxsignaling:toomanyquestionstoanswer.PlantCellEnviron,2012,35,259-270Osmoticstressasasecondarystress

Osmoticstress:akindofwaterstress

Osmoregulation/osmoticadjustment:Osmoprotectant/osmolyte/compatiblesoluteinorganicsolutesK+,Na+,Ca2+,etalorganicsolutesprolinesugars...ProlineaccumulationasanindexforstresstoleranceNewPhytol,2010,188,1001-1013PlantPhysiol,1999,120,391-400StressprotectionandinjuryrepairarefulfilledbysignaltransductionandgeneexpressionProteinswithdirectprotectivefunctionsHSP:HeatshockproteinsAFP:AntifreezeproteinsOsmotins:PRs:pathagen-relatedProteinsLEAproteinMetabolicpathwaysproducingprotectivemoleculesAntioxidantsOsmoticregulationsInorganicsolutes:Na+,K+,Ca2+、Mg2+、Cl-、NO3-、SO42-Organicsolutes:proline,betaines,sugars,aminoacidsPlanthormonesinstressresponsesAbscisicacidEthyleneJasmonatesSalicylicacidBrassinosteroidsImmediatetolerancemechanismsProtectingmechanismsenablebiochemicalandcellularprocessestofunctionproperlyprotectcellsfrombeinginjuredensurenormalgrowthanddevelopmentofplantsRepairingmechanismsforrescueAcclimationmechanismsgetbetterperformanceinsubsequentstresses5.StresstolerancemechanismsPlantstresssignaling:acommonmodelFourquestionraisedbyearlyresearchers:Howdoplantcellssensethestresses?Howarethestresssignalstransducedintocellularsignalsandtransmittedtothenucleus?Howisgenetranscriptionaffectedbythesestresssignals?Howdothegeneproductsfunctioninstresstolerance?Shinozaki,K.&Yamaguchi-Shinozaki,K.Molecularresponsestodroughtandcoldstress.CurrOpinBiotechnol,1996,7,161-167WaterDeficitStress

DroughtandosmoticstressCraterostigmaplantagineumLinderniabrevidensSelaginellatamariscina1.DecreasedLeafAreaIsanEarlyAdaptiveResponsetoWaterDeficitWaterstressresponsesDependenceofleafexpansiononleafturgor.2.WaterDeficitStimulatesLeafAbscission3.StomataCloseduringWaterDeficitinResponsetoAbscisicAcidAccumulationofABAbychloroplastsinthelight.4.WaterDeficitLimitsPhotosynthesiswithintheChloroplastEffectsofwaterstressonphotosynthesisandleafexpansionofsunflower(Helianthusannuus).Thisspeciesistypicalofmanyplantsinwhichleafexpansionisverysensitivetowaterstress,anditiscompletelyinhibitedundermildstresslevelsthathardlyaffectphotosyntheticrates.Waterlossandcarbongainbysugarbeet(Betavulgaris),anosmoticallyadjustingspecies,andcowpea(Vignaunguiculata),anonadjustingspeciesthatconserveswaterduringstressbystomatalclosure.1.Osmoregulation:AccumulationandFunctionsofCompatibleSolutesProlineSugarsCyclitols（环多醇）GlycineBetaineDrought&SalinityStressWaterstresstolerancemechanismsCurrOpinPlantBiol,2007,10,296-302Functionsofosmolytes:anycontributiontotolerance?RWCandfreeprolinecontentofTriticumandAegilopsgenotypessubjectedtodroughtstressfor2,4,6and8hPlantCellEnviron,2006,29,2143

FormationofReactiveMoleculesEnzymesThatDetoxifyAldehydesPeroxiredoxinsThioredoxinsProteinOxidationDrought&SalinityStress2.Antioxidativesystem:oxidativestressanddetoxifyingsystemLateEmbryogenesis-Abundant(LEA)ProteinsAquaporinsHeatShockProteins(Hsps)ProteasesandProteinaseInhibitorsDrought&SalinityStress3.Waterstress-inducedproteins:4.RolesofabscisicacidDrought&SalinityStressWild-typetobaccoaba2mutant(mutantofzep)aao3mutantsarewiltyWTaao3CurrOpinPlantBiol,2007,10,296-302SignalperceptionUnknowninplantsInyeast,hyperosmoticstressissensedbytwotypesofosmosensors,SLN1andSHO1,thatfeedfinallyintoHOG(high-osmolarityglycerol)MAPKpathway.SignaltransductionTranscriptionalregulationSignaltransductionStress-ResponsiveGenesAreRegulatedbyABA-DependentandABA-IndependentProcessesABAResponseElements(ABREs)TheDehydrationResponseElement(DRE)TranscriptionFactorsModulatedbyOsmoticStressBasicRegionLeucineZipper(bZIP)ProteinsHomeodomain-LeucineZipperProteins(HD-ZIP)Zn-FingerProteinsAP2/ERF-TypeTranscriptionFactorsMyb-LikeProteinsMyc-LikeProteinsCDT-1Drought&SalinityStressABA-dependentandABA-independentpathwaysSalt/Saline/SalinityStressSaltsinsoil:Neutralsalts:NaCl,Na2SO4...Alkalinesalts:Na2CO3,NaHCO3...Saltstressiscommonlycausedbyamixtureofsalts.NaClisthesuspectundermostconditions.Therefore,NaClstressisconsideredinmoststudies.However,duetothetoxicityofsinglesalt,weshouldprovideothersaltssuchK+inthesolution.Highsalinitycauses:hyper-ionicstresshyper-osmoticstressPlantsdifferintheirsalttolerancecapacities.SOS1,plasmamembraneNa+/H+antiporter;ACA,plasma/tonoplastmembraneCa2+-ATPase;KUP1/TRH1,high-affinityK+-H+co-transporter;atHKT1,sodiuminfluxtransporter;AKT1,K+inchannel;NSCC,nonselectivecationchannel;CAX1or2,Ca2+/H+antiporter;atNHX1,2or5,endomembraneNa+/H+antiporter.Membranetransportproteinsmediatingsodium,potassium,andcalciumtransportduringsalinitystress.Redarrowsindicatepositiveregulationoftheeffectedtransportproteinwhilebluearrowsindicatenegativeregulation.Proteinsshowninyellowareactivatedbysalinitystress.SOS1,plasmamembraneNa+/H+antiporter;SOS2,serine/threoninekinase;SOS3,Ca2+bindingprotein;HKT1,sodiuminfluxtransporter;AKT1,K+inchannel;NSCC,nonselectivecationchannel;NHX1,2or5,endomembraneNa+/H+antiporter;showninorangeisanunderterminedcalciumchannelprotein.TheregulationofionhomeostasisbytheSOSsignaltransductionpathway,salinitystress,andcalciumlevels.LowTemperatureStress

ChillingandFreezingStressCryo-CryobiologyCryoscopyCryoinjuryCryoprotectant(Cryoprotectivecompound)CryostorageColdacclimation冷驯化冷适应Coldtolerance/resistance抗冷性耐冷性ColdstressresponsesCarbohydratesBeganfrom19thCentury,sugarcontrolofpotatoinindustrySakaiA.SurvivaloftheTwigofWoodyPlantsat-196°C.Nature.1960.185(4710):393-394.WascorrelatedwithsugaraccumulationColdtolerantplants(varieties/cultivars)accumulatemoresugarsthancoldsensitiveonesOthercompatiblesolutesProlines,betaine,raffinoseandpolyaminesFlavonoidsflavonols,flavones,anthocyaninsandproanthocyanidinsMembranesystems:OrganelleMitochondriaChloroplastPlasmamembraneMembranecompositionFattyacidsLipidsAnti-freezeproteins(AFPs)抗冻蛋白的特性：影响冰晶形态。在纯水中，冰晶通常平行于晶格的基本面（α轴）生长而很少沿垂直方向（c轴）生长，因此冰晶平而圆。低浓度（µM）的抗冻蛋白可以抑制冰晶平行于α面生长，使冰晶形成棱角分明的六面体；而高浓度的抗冻蛋白则使冰晶主要沿c轴方向生长而形成六面体双棱锥形或针状晶体。