真菌學(xué)教學(xué)課件：chapter 4 The medicinal mushroom forest

Endophytes:MutualisticSymbiontsEndophytesareprimarilybenevolent,nonmycorrhizalfungithatpartnerwithmanyplants,fromgrassestotrees.Theirmyceliathreadbetweencellwallsbutdon’tenterthem,enhancingaplant’sgrowthandabilitytoabsorbnutrients,whilestavingoffparasites,infections,andpredationfrom

insects,otherfungi,andherbivores.

Endophyticfungiareespeciallyskilledatproducingspecializedtoxiccompounds.Endophytesinlargecrabgrass,forexample,appeartoproducetoxinsthatkillfireants,andthoseingrassessuchasthedarnelweed(Loliumtemulentum)causesleepinessincattleandhorses,afactlongknowntoranchersinCentralAmerica.

Endophytes,whichwereoncethoughttobepathogens,areincreasinglyviewedas

engagingtheplantinamutuallybeneficialrelationship.Ina2003experimentinPanama,researchers

foundthatwhenendophyte-freeleavesfromthechocolate-producingcocoatree(Theobromacacao)wereinoculatedwithendophytes,leafnecrosisandmortalitydeclinedthreefold,suggestingabiodefensiveeffectispossibleagainstotherpathogens.Accordingtooneestimate,morethan10,000sporesoffungilandoneachleafperday.Sporesfromendophytescompetewithmanyotherfree-flyingfungalspores.Amidstsuchcompetition,friendlyfungitakingupresidenceisactuallyanassettoplantsotherwisesubjecttopathogenicassault.WheatfarmersbenefitfromtheendophytePiriformosporaindica.Thisspeciesisaroot-basedendophytethatpromotesthegrowthofwheatshootsandrootsandiscapableofincreasingleafandseedproductionbymorethan30percentwhileshieldingrootsfrominfectionbypathogenicmicrobes.Furthermore,seedlingspairedwiththismutualistsuccessfullygerminated95percentofthe

time,comparedtoonly57percentforseedlingswithoutthisspecies.Thisspecieshasalsodemonstratedgrowth-enhancingpropertieswhenpairedwithmaize(Zeamays),tobacco

(Nicotianatobaccum),andparsley

(Petroselinumcrispum).Clearly,pairingthisandotherendophyteswithagriculturalcropscanincreaseyield,decreasedisease,andreducetheneedforfertilizersandinsecticides.

JoanHensonandotherresearchers(2004)filedapatentapplicationusingaCurvulariaspeciesisolatedfromgrassesinthegeothermalzonesofYellowstoneandLassenVolcanicnationalparks.

Henson’sresearchshowedthatgrassesinoculatedwiththisendophytesurvivedtemporaryexposuretoextraordinarily

hightemperatures—158°For70°C—whilethosewithoutshriveledanddied.Althoughwheatdidnotsurviveintheirexperiment,itdiddemonstrateincreaseddroughtresistance.WhenwatermelonseedlingsandmustardseedlingsweredustedwithCurvulariaspores,thesporesgerminatedandinhabitedtheyoungplants.Aftertheendophyticfungibecameestablishedontheirhosts,researchersexposedtheseedlingstoextremelyhightemperatures(122°For50°C).Theseedlingswiththeendophyticsporessurvivedprolongedexposures,butthesametypesofseedlingswithoutendophyticsporesdied.Forestdwellerslongagodiscoveredthevalueofmedicinalmushroomsforthehealingofboththebodyandtheforest.FungiasAlliesofPeopleandthePlanet

Wefaceescalatingchallengestoourhealthfrompollutionanddisease.Eveninthiseraofhightechgenomics,naturalcompoundsstillprovideabaselineforsynthesizingdrugs.Estimatesarethattwo-thirdsofourpharmaceuticalsstilloriginatefromnature.

Naturalmedicinessuchastaxol,discoveredinthebarkofPacificyewtrees(Taxusbrevifolia),givechemistscluestomanufacturingsimilarpotentcompoundsfortreatingdeadlydiseases,includingovarianandother

cancers.AndreaStierle,GaryStrobel,andDonaldStierle(1995)discoveredthatanendophytic

fungus,Taxomycesandreanae,inhabitingtheyewtreesynthesizedtaxol,andforthisdiscoverythey

wereawardedseveralpatents.

AnextractofthemyceliumfromthemushroomFomitopsisofficinalisprotectshumanbloodcellsfrominfectionbyorthopoxviruses,thefamilyofvirusesthat

includessmallpox(Stamets2005b).

Agarikonisrestrictedtoanendangeredhabitatinrapiddecline.Lessthan5percentofournorthwesternold-growthforestssurvivetoday,intheaftermathof150yearsoflogging.Theold-growthmycoforestssuddenlybecomemorevaluablenotasatimbersourcebutasaremedyagainstnaturalorweaponizeddiseases.

Whatothermycomedicalremediesawaitdiscoveryinourancientforests?Ihavelittledoubtthatmanyothermushroomswillprovideuswithantiviraloranticancerdrugs.

Manymushrooms

arenowknowntohavemedicinalpropertiesusefulforimprovinghumanhealth.

Althoughmyceliumhasjustasinglecellwallprotectingitfromhundredsofmillionsofhostilemicrobesineverygramofsoil,itmanagestoformnetworksextending,insomedocumentedcases,thousandsofacresandweighingthousandsoftons.Nutrientrichmushrooms,beforesporulation,resistinfectionandrot.

Howdomushroomsandmyceliumdothis?Thecellsurfaceofmycelium“sweats”outantibioticsthatareknowninthefieldasexudatesorsecondarymetabolites.

Mushroommyceliaexudedropletscontainingenzymesandantibioticsandprofusewater.

Usefulantibioticsisolatedinmushroomsincludecalvacinfromgiantpuffballs(Calvatia

gigantea),armillaricacidfromhoneymushrooms(Armillariamellea),campestrinfrommeadow

mushrooms(Agaricuscampestris),coprinolfrominkycaps(Coprinusspecies),corolinfromturkey

tailmushrooms(Trametesversicolor=Coriolusversicolor),cortinellinfromshiitake(Lentinula

edodes),ganomycinfromreishi(Ganodermalucidum),agaricinfromagarikon(Fomitopsis

officinalis)andsparassolfromcauliflowermushrooms(Sparassiscrispa).

MedicinalMushroomsforHealingForestsandFightingFungalBlightsAblightisaspecies-specificparasiticinvasionbyafungusthatkillsmanymembersofthetargetspeciesinacommunity.Fungalblightscanfellaforestoffirsandoaksinamatterofmonths.Nonblightingfungi,whichalsohavemedicinalornutritionalusesforhumans,maybethebestdefenseagainstblightingfungi.Diseaseblightscaninflictmassiveeconomicdamageonthetimbervalueofforests,buttheymayactuallybebeneficial,especiallywhenviewedoverthelongterm.

Honeymushrooms(Armillariaostoyae,Armillariagallica,andArmillariamellea)willattackatree,

causingdevastatingrootrotandhollowbrowncorerot.Asthediseasedtreesintheforestdie,the

wooddriesandmaycatchfireifstruckbylightning,especiallyiflocatedonridgetops.Theforestfireoftencauterizesthesoil,killingtheArmillaria

thatoriginallykilledtheforest.Theresultmaybehighmountainmeadowsinhabitedbygrassuntilanewforestregenerates.Fireshelpcreatemeadowswhich,duetotheirlowwoodcontent,providefirebreaksandforestdisease–freezones.Thiscycle

offoresttomeadowtoforestmaybehealthierfortheecosysteminthelongrunbecausewitheachsuccessionthesoilbiosphereisenrichedassoilsthicken.Theintroductionofselectsaprophyticorendophyticspeciescanforestallthe

spreadofparasiticspeciesthatcauseblights.InWesternAustralia,inoculatingkarri(Eucalyptusdiversicolor)stumps,PearceandMalajczuk(1990)foundthatHypholoma

provedtobecompetitiveagainstArmillaria,insomecasesexcludingitentirely.Theyhavebeenamongthefirstresearcherstotesttheideaoffightingamushroomblightwithanothermushroom.

InBritishColumbia,Chapmanandcolleagues(2004)buriedHypholomafasiculareintheformofsawdustspawnintherootzonesofstumps.Theyfoundthatafter5yearsArmillariarootrotdiseaseinseedlingsoflodgepolepine(Pinuscontorta)andDouglasfirs(Pseudotsugamenziesii)wassignificantlyreduced—upto67percent.

OthermushroomsmightalsoproveusefulindefendingforestsfromArmillariablights.Cauliflowermushrooms(Sparassiscrispa)secretetheantifungalantibioticsparassol,ororsellinicacid.Thissuggestsanantifungalstrategyforforesterstoconsider.Inprinciple,mushroomslikecauliflowerscoulddefendforestsagainstblightsbyArmillaria;inoculatingstumpsattheperimeterofanArmillariablightcouldlimitfurtherspreadofthisdestructiveforestdisease.Laboratorytestsshowthepromiseofthisblight-blockingscenario.Whenastrainofparasitichoneymushroomsisculturedinthesamepetridishwithastrainofcauliflowermushroom,thecaulifloweroutcompetesandappearstoparasitizethehoneymushroom.

OthermushroomsthatoutcompeteArmillariarootrotarethemedicinallyactiveturkeytails

(Trametesversicolor);s