331 FruitingBodyDevelopment 333 AEnvironmentalFactors333 1NutrientsandRelatedFactors333 2PhysicalFactors334 BEndogenousFactors ID: 93030
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...............331 II.PhysiologicalFactorsInuencing Fruiting-BodyDevelopment .............333 A.EnvironmentalFactors...............333 1.NutrientsandRelatedFactors.......333 2.PhysicalFactors..................334 B.EndogenousFactors.................336 1.MetabolicProcesses...............336 2.Pheromones.....................338 III.SignalTransductionCascades ............339 A.PerceptionofEnvironmental andEndogenousSignals.............339 1.Chitin............ ..............346 2.Carbohydrates...................346 3.Pigments.......................347 4.CellWallProteins.................347 5.AreMultipleGenes withOverlappingFunctionsInvolved inCellWallMetabolism?...........348 V.Conclusions ..........................348 References........... ................348 1 LehrstuhlfürAllgemeineundMolekulareBotanik,Ruhr-Univer- sitätBochum,44780Bochum,Germany distinctgroups:(1)thesaccharomycetes,whichare mostlyunicellular,and(2)mycelialascomycetes, themajorityofwhichshareseveralcharacteristics includingcertaincellwallconstituents,septal poreswithWoroninbodies,andadikaryoticphase aspartoftheirlifecycle.Mycelialascomycetes typicallyformfruitingbodiescalledascomata orascocarps(Alexopoulosetal.1996;Barr 2001).Thesearehighlycomplex,multicellular structurescomposedofmanydifferentcelltypes thatsurroundtheasciinacharacteristicmanner specialenvironmentalconditionsandiscontrolled bymanydevelopmentallyregulatedgenes.This chaptergivesaconciseoverviewonthebasicsof fruiting-bodydevelopmentinhyphalascomycetes, focusingonaspectsrelevantfortaxonomyand morphology,anditsummarizesenvironmental TheMycotaI Growth,DifferentationandSexuality Kües/Fischer(Eds.) ©Springer-VerlagBerlinHeidelberg2006 328S.Pöggeleretal. Table.16.1. Genesinvolvedinfruiting-bodydevelopment OrganismsGeneGeneproductDefectofmutantsReference Neurospora crassa asd-1 RhamnogalacturonaseNoascosporesNelsonetal.(1997b) ndk-1 Nucleosidediphosphate kinase Light-dependent positioningofperithecia Oguraetal.(2001) sod-1 SuperoxiddismutaseLight-dependent positioningofperithecia Yoshidaand Hasunuma(2004) nuo12.3, nuo20.8, nuo30.4, nuo78, nuo51, nuo24, nuo2 Subunitofrespiratory chainNADHdehydrogenase NoascosporesFeckeetal.(1994), Duarteetal.(1998), Almeidaetal.(1999), DuarteandVideira(2000) mfa-1 Hydrophobicpeptide pheromone Malesterility,aberrant femalesexualdevelopment andascosporeproduction Kimetal.(2002a) pre-1 GPRC,pheromonereceptorFemalesterilityKimandBorkovich(2004) gna-1 Gprotein subunitFemale-sterile,noperitheciaIveyetal.(1996), YangandBorkovich(1999) gna-3 Gprotein subunitSmallerperitheciawithnobeaks, reducednumberofascospores Kaysetal.(2000) gnb-1 Gprotein subunitFemale-sterile,noperitheciaYangetal.(2002) gng-1 Gprotein subunitFemale-sterile,noperitheciaKrystofovaand Borkovich(2005) krev-1 GTP/GDP-bindingprotein; memberoftherassuperfamily NoperitheciaItoetal.(1997) cr-1 AdenylylcyclaseDelayedperithecia andascosporeformation Perkinsetal.(1982), Iveyetal.(2002) mak-2 MAPK,related to S.cerevisiae Fus3p andKss1p Female-sterile, noprotoperithecia Pandeyetal.(2004), Lietal.(2005) nrc-1 MAPKKK,similar to S.cerevisiae Ste11p Female-sterile, noprotoperithecia KotheandFree(1998) nrc-2 Serine-threonineprotein kinase Female-sterile, noprotoperithecia KotheandFree(1998) rgb-1 Bregulatorysubunitofthe type2ASer/Thrphosphatase Female-sterile, noprothoperithecia YatzkanandYarden(1999) ham-2 Putativetransmembrane protein Female-sterile, noprotoperithecia Xiangetal.(2002) eat-2 Highlysimilartoadomain presentintheplasma membraneATPase Female-sterile, noprothoperithecia Randalland Metzenberg(1998) cel-2 subunitoffatty acidsynthase Fewerperitecia,rareascosporesGoodrich-Tanrikulu etal.(1999) asm-1 Transcriptionfactorwith APSESdomain Female-sterile, noprotoperithecia Aramayoetal.(1996) vma-1 SubunitAoftheV-ATPaseFemale-sterile, noprotoperithecia, cannotdonatenucleiinacross Bowmanetal.(2000) cpc-2 WD-repeatproteinrequired torepressgeneralamino acidcontrol,scaffoldprotein Female-sterile, noprotoperithecia Mülleretal.(1995) rco-1 Multidomainproteinthat mediatestranscriptional repression Female-sterile, noprotoperithecia Yamashiroetal.(1996) asd-4 GATA-typezincnger transcriptionfactor Noasci,noascosporesFengetal.(2000) wc-1 GATA-likezincnger transcriptionfactor Nophototropism ofperithecialbeaks Ballarioetal.(1996), OdaandHasunuma(1997) FruitingBodiesinAscomycetes329 Table.16.1. (continued) OrganismsGeneGeneproductDefectofmutantsReference wc-2 GATA-likezincnger transcriptionfactor Nophototropism ofperithecialbeaks LindenandMacino(1997), OdaandHasunuma(1997) pp-1 Transcriptionfactor homeodomain,C 2 H 2 zinc nger,Ste12phomolog NoprotoperitheciaLietal.(2005) Podospora anserina car1 Peroxisomalmembrane protein Impairedkaryogamy, noascospores Berteaux-Lecellieretal. (1995) cro1 Cytosolicprotein withC 2 H 2 zincngermotif Impairedmeiosis, noascospores Berteaux-Lecellieretal. (1998) AS4 Translation-elongation factorEF-1 ,eF1A Noascospores, noperithecia Silaretal.(2001) su1 Translation-termination factoreRF3 Female-sterile, noprotoperithecia GagnyandSilar(1998) su2 Translation-termination factoreRF1 Female-sterile, noprotoperithecia GagnyandSilar(1998) PaCox17 Chaperonetargetingcopper tocytochromec Delayedperithecialformation andreducedascusformation Stumpferletal.(2004) rmp1 Nohomology,functions innucleus mitochondria cross-talk Lethalorwithoutmitochondrial targetingsequence,noascospores Contamineetal.(2004) PaNox1 NADPHoxidaseNoperitheciaMalagnacetal.(2004) PaNox2 NADPHoxidaseNoascosporegerminationMalagnacetal.(2004) mod-A Proline-richprotein withSH3-bindingmotif Female-sterile, noprotoperithecia Barreauetal.(1998) mod-E Heat-shockproteinHSP90Sterileperithecia,noascosporesLoubradouetal.(1997) mfp Hydrophobicpeptide pheromone Male-sterileCoppinetal.(2005) mfm PeptidepheromoneMale-sterileCoppinetal.(2005) mod-D Gprotein subunitFemale-sterile, noprotoperithecia Loubradouetal.(1999) PaAsk1 MAPKKK,similar to S.cerevisiae Bck1p NoperitheciaKickaandSilar(2004) grisea Copper-activated transcriptionfactor, orthologoftheyeast transcriptionfactorMAC1 Female-sterile, noprotoperithecia Osiewaczand Nuber(1996), Borghoutsand Osiewacz(1998) e1 Transcriptionfactor, C 2 H 2 zincnger Fewermicroconidia,more abundantprotoperithecia Coppin(2002) pah1 Transcriptionfactor, homeoboxprotein Enhancednumberof microconidia,delayed protoperitheciadevelopment Arnaiseetal.(2001) ami1 Homologof A.nidulans APS-A Male-sterile,delayed fruiting-bodyformation Graiaetal.(2000) Sordaria macrospora pro11 WD-repeatproteinNoperitheciaPöggelerandKück(2004) pro4 LeucinebiosynthesisNoperitheciaKück(2005) acl1 SubunitofATP-citrate-lyaseNoascosporesNowrousianetal.(1999) spo76 ChromosomalproteinImpairedmeiosis,fewascosporesvanHeemstetal.(1999) pro1 C 6 zincngertranscription factor NoperitheciaMasloffetal.(1999) Aspergillus nidulans trpB TryptophanebiosynthesisNocleistotheciaEckertetal.(1999,2000) hisB HistidinebiosynthesisNocleistotheciaBuschetal.(2001) tubB -tubulinNoascosporesKirkandMorris(1991) uvsC DNA-repairenzyme homologof S.cerevisiae RAD51 Nokaryogamy,noascosporesvanHeemstetal.(1997) lsdA Nosequencesimilarity, unknownfunction Noinhibitionofcleistothecia developmentunderhighsalt conditions Leeetal.(2001) 330S.Pöggeleretal. Table.16.1. (continued) OrganismsGeneGeneproductDefectofmutantsReference phoA Cyclin-dependentkinaseEnhancednumberofcleistothecia underphosphorus-limited conditions BussinkandOsmani(1998) pho80 Putativecyclin-dependent kinaseinhibitor PromotessexualdevelopmentWuetal.(2004) csnD SubunitofCOP9signalosomeNocleistotheciaBuschetal.(2003) veA Nohomology,unknownNocleistotheciaKimetal.(2002b) noxA NADPHoxidaseNocleistotheciaLara-Ortízetal.(2003) ppoA Putativefattyacid dioxygenase Increasedratioofasexual tosexualdevelopment Tsitsigiannisetal.(2004) odeA -12desaturaseDelayedascosporogenesisCalvoetal.(2001) gprA GPRC,pheromonereceptorFewercleistotheciaandascosporesSeoetal.(2004) gprB GPRC,pheromonereceptorFewercleistotheciaandascosporesSeoetal.(2004) gprD GPRCNocleistotheciaHanetal.(2004) fadA Gprotein subunitNocleistotheciaRosènetal.(1999) sfdA Gprotein subunitNocleistothecia,moreHüllecellsRosènetal.(1999) bA RGSproteinNocleistotheciaHanetal.(2001) sakA MAPK,similar to S.cerevisiae Hog1p Prematuresexualdevelopment, morecleistothecia Kawasakietal.(2002) steC MAPKKK,similar to S.cerevisiae Ste11p NocleistotheciaWeietal.(2003) steA Transcriptionfactor homeodomain,C 2 H 2 zinc nger,Ste12phomolog Nocleistothecia, onlyHüllecells Vallimetal.(2000) nsdD Transcriptionfactor GATA-type Nocleistothecia,noHüllecellsHanetal.(2001) stuA Transcriptionfactor withAPSESdomain Nocleistothecia,noHüllecellsWuandMiller(1997) dopA Putativetranscription factor,leucinezipper-like domainsandsimilarity toC/EBPtranscriptionfactor Nocleistothecia,noHüllecellsPasconCastiglioniand Miller(2000) medA TranscriptionalregulatorNocleistothecia,onlyHüllecellsBusbyetal.(1996) cpcA Transcriptionfactor, c-Jun-likeleucinezipper, requiredtoactivategeneral aminoacidcontrol Whenoverexpressed, nocleistothecia Hoffmannetal.(2001b) cpcB WD-repeatprotein,required torepressgeneralamino acidcontrol,scaffoldprotein NocleistotheciaHoffmannetal.(2000) Magnaporthe grisea magA Gprotein subunitNoascosporesLiuandDean(1997) magC Gprotein subunitNoascosporesLiuandDean(1997) magB Gprotein subunitFemale-sterile,noperitheciaLiuandDean(1997) mac-1 AdenylylcyclaseFemale-sterile,noperitheciaChoiandDean(1997) mps-1 MAPK,similar to S.cerevisiae Sltp Female-sterile,noperitheciaXuetal.(1998) Cryphonectria parasitica Mf2-2 Hydrophobicpeptide pheromone FemalesterilityZhangetal.(1993) Mf1-1 PeptidepheromoneMale-sterileTurinaetal.(2003) cpg-1 Gprotein subunitFemale-sterileGaoandNuss(1996) cpg-2 Gprotein subunitEnhancedperithecialdevelopmentGaoandNuss(1996) Fusarium graminearum mgv-1 MAPK,similar to S.cerevisiae Sltp Female-sterile,noperitheciaHouetal.(2002) Cochliobolus heterostrophus cga-1 Gprotein subunitFemalesterilityHorwitzetal.(1999) chk-1 MAPK,relatedto S.cerevisiae Fus3pandKss1p FemalesterilityLevetal.(1998) FruitingBodiesinAscomycetes331 (Raju1992).Whenmale-sterilemutantsareused asfertilizingparent,perithecialdevelopment isinitiated,butthenarrestedatanearlystage. In N.crassa ,numerousfemale-sterilemutants thatdonotformfunctionalprotoperitheciaor displayareducedfertilityhavebeendescribed. Becauseofthishighfrequencyofsterilityin femalestrains,itwassuggestedthatatleast400 genesarerequiredforperitheciumandascospore developmentin N.crassa (Johnson1978;Leslieand Raju1985).However,manyofthesefemale-sterile mutantsshowabnormalvegetativegrowth,and thusthisfemalesterilitymaybeaconsequence ofamorphologicaldefect,ratherthanamutation inagenespecicallyneededforfruiting-body differentiation(Raju1992). Effectivemoleculartechniquesdevelopedfor N.crassa ,suchasthetransformationandcreation ofcosmidgenomiclibrariesinvolving,forexam- ple,phenotypiccomplementation,haveledtothe cloningandfunctionalcharacterizationofregu- latorygenesthataffectmorphology(Baileyand Ebbole1998).Othermoleculargeneticapproaches usedsubtractivehybridizationtoisolate N.crassa sexualdevelopmentalgenes. Withthisattempt,NelsonandMetzenberg (1992)succeededinidentifying14genestran- scribedonlyundernitrogen-depletinggrowth conditions.Oneofthese, asd-1 ,hasbeenshownto encodeaputativerhamnogalacturonasenecessary forascusdevelopment(Nelsonetal.1997b). Inlarge-scaleanalyses,fruitingbody-specic expressedsequencetags(ESTs)from N.crassa weresequencedforfurthermolecularcharacteri- zation(Nelsonetal.1997a).Insuchexperimental approaches,isolatedcandidategeneshavetobe inactivatedtoobtaindetailedinformationabout mutantphenotypesandgenefunction. Inactivationofdevelopmentalgenesin N. crassa wasachievedeitherbyhomologousrecom- binationorbygenesilencingviarepeat-induced pointmutation(RIP).The N.crassa RIPprocess efcientlydetectsandmutatesbothcopiesofase- quenceduplication.RIPactsduringthedikaryotic stageofthesexualcycle,causingnumerousC:G- to-T:Atransitionswithinduplicatedsequences, andisfrequentlyusedtoinactivategenesin N. crassa (GalaganandSelker2004).Finally,the wholegenomesequenceof N.crassa hasbecome available,openingtheopportunityforanalyzing genesinvolvedinfruiting-bodydevelopmentby meansofreversegeneticapproaches(Galagan etal.2003;Borkovichetal.2004). 2. Sordariamacrospora Intheheterothallicspecies N.crassa ,mutations conferringmaleand/orfemalesterilitycanbe detecteddirectlybecauseoftheirsterilityeffects inheterozygouscrosses.However,recessivemu- tationsthataffectpost-fertilizationperithecial developmentwillremainundetectedinheterothal- licspeciesuntilthemutantalleleisavailablein bothmatingtypes,thusallowinghomozygous crosses.Incontrastto N.crassa ,thehomothallic pyrenomycete S.macrospora isself-fertile,which meansthatrecessivemutationscandirectlybe testedfordefectsinfruiting-bodydevelopment. Moreover, S.macrospora producesonlymeioti- callyderivedascospores,whereasasexualspores, suchasconidia,areabsent.Thus,thereisno interferencebetweentwodifferentdevelopmental programs,whichmakesiteasier,forexample,to analyzedifferentiallyexpressedgenesinvolvedin ascocarpdevelopment.Underlaboratorycondi- tions,peritheciaandascosporesreachmaturity within7daysafterascosporegermination.During thisdevelopment,distinctreproductivestructures, suchasascogonia,protoperithecia(youngfruiting bodies),andperithecia,canbedistinguished (Fig.16.2).Because S.macrospora represents suchafavorablegeneticsystemforscientists,this homothallicpyrenomycetewasusedtogenerate numerousmutantsthatareblockedatvarious stagesofperithecialdevelopment(Esserand Straub1958;Masloffetal.1999).Wild-typestrains of S.macrospora areself-fertileandproduce perithecia.However,fertileperitheciaarealso formedincrossesbetweensterilestrains,when nucleiareinterchangedbyhyphalanastomoses atthecontactzonesoftwosterilemycelia.These crossesfacilitatetheanalysisofepistaticrela- tionshipsamongdevelopmentalmutants.The establishmentofmoleculartoolsprovidesthe basisforstudyingfruiting-bodydevelopmentin S. macrospora (WalzandKück1995;Pöggeleretal. 1997). 3. Aspergillusnidulans Theplectomycete Aspergillusnidulans (teleo- morph: Emericellanidulans )propagatesbythe formationofsporesthatcanbeeitherasexualor sexual,andhaslongservedasamodelsystemfor understandingthegeneticregulationofasexual developmentinascomycetes(Adamsetal.1998). Theasexualcycleischaracterizedbytheproduc- 332S.Pöggeleretal. Fig.16.2. Sexualdevelopmentof Sordariamacrospora . A , B Youngascogonium; C , D ascogonium; E , F protoperithecium; G perithecium; H topviewofperithecium,withascospores. A , C , E Differentialinterferencecontrastlightmicrographs DIC. B , D , F Fluorescencemicrographsof A , C ,and E with DAPIstainingofnuclei. G , H Scanningelectronmicrographs tionofhaploidconidiophoresthatbearasexual, single-celledsporescalledconidia(Fischer2002, seeFischerandKües,Chap.14,thisvolume). Sexualdevelopmentof A.nidulans startsafter conidiophoredifferentiation.Theconidiophores areproducedbymitoticdivisionin3daysafter germination,whereasthesexualascosporesare formedafteratleast7days(Pontecorvo1953). A.nidulans ishomothallic,andasinglecolony canproducecleistothecialledwithupto1000 ascosporesbyself-fertilization. In A.nidulans ,noobviousantheridiumoras- cogoniumstructurescanbeobserved(Benjamin 1955).Itwas,however,assumedbyKwonandRaper (1967)thatin Aspergillusheterothallicus ,ahet- erothallicrelativeof A.nidulans ,acoiledstructure equivalenttoanascogoniumfusestoasecondcell equivalenttoanantheridium. Incontrasttopyrenomycetes,thepresumptive ascogoniumof A.nidulans isnotsurroundedby sterilehyphae,andpre-fruitingbodiesarenot formed.Onlyafterfertilizationistheascogonium surroundedbygrowing,unorderedhyphae,which formanincreasinglypackednestandthen differentiateglobose,multinucleateHüllecells, whichsupportthedevelopmentofcleistothecia (Ellisetal.1973).Thesurroundinghyphae thatformthenestlaterdifferentiateintothe cleistothecialenvelope.Thedevelopingspherical cleistotheciaarelledwithascogenoushyphae thatdifferentiateintoasci.Afterkaryogamy,the zygotestageisimmediatelyfollowedbymeiosis. Directlyaftermeiosis,thefourresultingnuclei passthrougharstpost-meioticmitosis.The eightnucleiarethenseparatedbymembranes,and giverisetoeightred-pigmentedascosporeswithin eachascus.Assecondpost-meioticmitosisresults ineightbinucleate,matureascospores(Brausetal. 2002).Similarlytothehomothallicpyrenomycete S.macrospora ,self-fertile A.nidulans strains canbeusedincrossingexperiments.Inthis case,hyphaefromtwodifferentstrainscanform anastomosesandexchangenucleiwhengrowing sufcientlyclosetoeachother(Hoffmannetal. 2001a). Thecoexistenceofsexualandasexualrepro- ductionwithinoneandthesameindividualhas made A.nidulans apopulargeneticmodelorgan- ismtocomparetnesseffectsofsexualandasexual reproduction.Becauseofitshomothallism,thesex- ualandasexualoffspringof A.nidulans havelargely identicalgenotypes.AswasshownbyBruggeman etal.(2003,2004),slightlydeleteriousmutations accumulateatalowerrateinthesexualthaninthe asexualpathway. Inadditiontoclassicalgenetics,various toolsrequiredformolecularbiologyhavebeen developed,andrecentlytheentiregenomeof A. nidulans hasbeensequenced(http://www.broad. mit.edu/annotation/fungi/aspergillus),thusmak- ing A.nidulans anexcellentmodelforstudying variousbiologicalquestions,includingthe multicellularcleistotheciumdevelopment. Forthegeneticdissectionofsexualsporula- tionin A.nidulans ,acollectionofascospore-less mutantswasisolatedbySwartetal.(2001).Toun- derstandthesexualreproductionof A.nidulans in moredetail,Hanetal.(1990)identiednumerous mutantsthatweredefectiveinsexualdevelopment inaforwardgeneticscreen.Thesewereclassied intotwogroups: