第七章植物的生殖生理课件

《第七章植物的生殖生理课件》由会员分享，可在线阅读，更多相关《第七章植物的生殖生理课件（77页珍藏版）》请在装配图网上搜索。

1、1Plant ReproductionZichao Mao 2Life cycle of plant 3Transition to reproductionFlower organ developmentGametogenesis and fertilizationPlant Reproduction4Transition to reproductionVegetative phaseReproductive phaseInflorescenceFlower5Production of flowers involves two transitions in ArabidopsisSC:stem

2、 cellP:organ primordiaSe:sepal1.Convert SAM（Shoot Apical Meristem)to inflorescence meristem(infinite,making lateral organs)2.Convert inflorescence meristem to floral meristem(terminal,flowers)6Factors regulating the transitionsVegetative meristemInflorescence meristemFloral meristemGenes(flowering-t

3、ime genes and floral identity genes)Light(photoperiod)The biological clockTemperature Hormones 7affecting the transition of vegetative growth to reproductive growthWTemf2Flowering-time genesemf1embryonic flower8affecting formation of inflorescence and floral meristemsFloral identity genesInflorescen

4、ce(from Inflorescence meristem)Flower(from Floral meristem)9terminal flower 1(tfl1):Convert the inflorescence meristem to the flower meristem.leafy(lfy):produce more inflorescences,delayed floweringMutations in floral identity genestfl1FUNCTION Controls inflorescence meristem identity and is require

5、d for maintenance of a indeterminate inflorescence.Prevents the expression of APETALA1 and LEAFY.Also plays a role in the regulation of the time of flowering in the long-day flowering pathway.May form complexes with phosphorylated ligands by interfering with kinases and their effectors Expressed bel

6、ow the apical dome of inflorescence and coflorescence meristems,and in inflorescence stem.Weakly expressed in vegetative phase from day 2 or day 3.Increased expression after commitment to flowering from day 7 on.LEAFY;LFY,FUNCTIONS IN:chromatin DNA binding,transcription factor activity,sequence-spec

7、ific DNA binding;INVOLVED IN:flower development,maintenance of inflorescence meristem identity,response to gibberellin stimulus,gibberellic acid mediated signaling;LOCATED IN:nucleus;EXPRESSED IN:shoot apex,leaf whorl,embryo,flower,seed;EXPRESSED DURING:7 growth stages;12Factors regulating the trans

8、ition to reproductionVegetative meristemInflorescence meristemFloral meristemEMFTF1LFY13Garner and Allard(1920s)The discovery of photoperiodismSoybeans(Glycine max)planted over a three-month period all flowered about the same time14Many more experiments were followed:Eliminate a variety of environme

9、ntal conditions:Nutrition,temperature,and light intensityRelative length of day and night decides the flowering timePhotoperiodism:ability of an organism to measure the proportion of daylight during a 24-hour period 15Varies according to the latitude and seasonal changes.Photoperiod16Critical daylen

10、gthCriticalDaylength(CD)Xanthium(苍耳）:a short day plant,flowers when CD is LESS than 15.5 hours.Hyoscyamus(茛菪):a long day plant,flowers when CD is MORE than 11 hours.17Plants are induced to flower by different photoperiodsshort day(SD):plants are stimulated to flower when the length of day falls belo

11、w a thresholdlong day(LD):plants are stimulated to flower when the length of day exceeds a thresholdDay neutral(DN):plants flower indifference to the changes of day length.Long-short-day:flowering requires certain number of short days are preceded by a certain number of long days.Short-long-day:flow

12、ering requires certain number of long days are preceded by a certain number of short days.Intermediate-daylength:not flowering if the daylength is too short or too long.Plants that respond to lengthening days and flower in the spring or early summer are known as long-day(LD)plants.Short-day(SD)plant

13、s flower in the late summer or autumn in response to shortening days and lengthening nights 19Do plants really measure the length of the daylength?20Xanthium flowers when the dark period exceeds 8.5 hours.Hamner and Bonner(1938):Xanthium strumarium(苍耳）,a SD plant with CD=15.5 hoursShort interruption

14、 of dark period,even by a pulse of light as short as 1 minute delays flowering.The relative length of dark is not the determining factor.21Similar results were obtained with other SD plants.For LD plantsA longer dark period inhibits flowering.Light break induces flowering.22What tissues/organs perce

15、ive photoperiod?23Exp.1:The leaf or apex of Perilla（紫苏）(a short day plant)was exposed to different daylength.24Exp.2:Grafting experiment with Perilla25the flowering signal is generated in the leafthe signal goes one way:from the leaf to the apexGrafting transmittableThe flowering signal:florigen?veg

16、etative or reproductive growth?SAMFlorigenFlorigenFlorigen Recent studies in Arabidopsis and rice have made a strong case that florigen,or at least acomponent of the floral stimulus,is the floral integrator FT.The FT gene is expressed in leaves,and the protein travels to the meristem where it intera

17、cts with another integrator,FD,to initiate the floral transition FT-like genes(FD,FVE,FCA,FY,and FPA)are ubiquitous in plants and have been found to regulate flowering in a variety of species including wheat and poplarThe role of phytochrome in de-etiolation responsePhytochrome:a molecular switching

18、 mechanismThe effect of light on the biological clockwPhytoperiodismPhytoperiodism and control of flowering and control of floweringwShort-day plant:required a light period shorter than Short-day plant:required a light period shorter than a critical length to flowera critical length to flowerwlong-d

19、ay plant:required a light period longer than a long-day plant:required a light period longer than a critical length to flowercritical length to flowerwDay-neutral plant:unaffected by photoperiod and Day-neutral plant:unaffected by photoperiod and flower when reaching a certain stage of maturityflowe

20、r when reaching a certain stage of maturitywVernalizationVernalization:use of pretreatment with cold to:use of pretreatment with cold to induce floweringinduce flowering32The Arabidopsis biological clockThe central oscillator:CCA1,LHY,and TOC1(these are transcription factors)and other proteins33Pres

21、ent in plants,animals,fungi,and some photosynthetic bacteriaAn internal time measuring system(“clock”)that runs on its own with a periodicity of nearly 24 hours.It can be“reset”by external signals.The biological clockTemperatureBiological clocks andcircadian rhythms36The Arabidopsis biological clock

22、 CCA1 and LHY are expressed during the day and together repress expression of TOC1 during the dayTOC1 is expressed at night and is required for activation of CCA1 and LHY1,beginning just before morning37Lack of the nyctinastic movement:diurnal rise and fall of leavesAltered flowering time in some mu

23、tantscca1:early floweringlhy:early floweringtoc1:early floweringSome other clock mutants can be late flowering Mutations in the clock genes38Temperature:VernalizationVernalization:low temperature treatment can promote flowering in some plants.The vernalization-effective temperature and duration of l

24、ow temperature treatment may vary.Vernalization is perceived by the shoot apex.The vernalization state is grafting transmissible.Definition the acquisition or acceleration of the ability to flower by a chilling treatmentPlants have evolved many systems to sense their environment and to modify their

25、growth and development accordingly.One example is vernalization,the process by which flowering is promoted as plants sense exposure to the cold temperatures of winter.A requirement for vernalization is an adaptive trait that helps prevent flowering before winter and permits flowering in the favorabl

26、e conditions of spring.In Arabidopsis and cereals,vernalization results in the suppression of genes that repress flowering.We describe recent progress in understanding the molecular basis of this suppression.In Arabidopsis,vernalization involves the recruitment of chromatin-modifying complexes to a

27、clade of flowering repressors that are silenced epigenetically via histone modifications.vernalization41Can be induced quicklyIncreases plant resistance to freezing stressDoes not affect flowering time.Cold acclimationVenalization in cerealsMachanism of Vernalization Vernalization-mediated changes i

28、n FLC chromatin.(a)Prior to cold exposure,FLC is actively expressed.The complexes that maintain this active chromatin conformation include the PAF complex,which methylates histone 3 tails at lysine 4 and 36(H3K4triMe and H3K36triMe),a SWR1-like complex,which deposits a histone 2A variant in the nucl

29、eosomes of FLC chromatin,and H2B ubiquitinases like HUB1 and HUB2 that ubiquitinate histone 2B tails(H2Bub1).Although FLC is in an active state,there are repressive complexes present such as Polycomb Repression Complex 2 and some degree of lysine 27 methylation of histone 3(H3K27triMea repressive mo

30、dification)(b)During cold exposure,FLC repression is initiated.VIN3 is induced,VIN3 and VIL1/VRN5 associate with the Polycomb complex,the density of repressive chromatin modifications such as lysine 27 methylation of histone 3 increases,and repressors such as LIKE HETEROCHROMATIN PROTEIN 1(LHP1)asse

31、mble on FLC chromatin.(c)As vernalization proceeds,the density of repressive modifications,particularly H3K27triMe and lysine 9 methylation of histone 3 H3K9triMe;mediated by an unknown H3K9 methyltransferase(HMTase)increases.(d)Eventually,a mitotically stable state of repression that no longer requ

32、ires VIN3 is achieved.This mitotically stable state is likely to involve positive feedback loops in which the repressive chromatin modifications serve to recruit the chromatin-modifying complexes including VRN1 to maintain a repressive state.As the FLC locus passes to the next generation,the active

33、chromatin state represented in(a)is re-established 47Hormone GA regulates flowering timeGA1:an enzyme involved in GA biosynthesisga1:In addition to the dwarf phenotype,the mutant flowers late under LD conditions and does not flower under SD conditions.GA treatment promotes flowering time.48Flower de

34、velopment in ArabidopsisVegetative meristemInflorescence meristemFloral meristemFlower:sepals,petals,stamens,and carpelsTransition to reproduction:Genes&other factorsFlower organ development:Organ identity genesOne of the early successes of the application of molecular genetics to study plant develo

35、pment was the discovery of a series of genes that act together,in an apparently simple combinatorial model,to specify the identity of the different organs of a flower.Widely known as the ABC model,The cast list of genes has been defined and,great progress has been made in understanding how they are

36、regulated,how they act together,what they do and how they have contributed to the evolution of the flower in its varied forms.51Flower organspetalstamencarpelsepal52The flower is generated from the floral meristem the floral meristem53Produced in 4 concentric whorls with the same ordersepal(whorl 1)

37、stamen(whorl 3)petal(whorl 2)carpel(whorl 4)Flower organs ABC model 55(the ap1 mutant is similar)stamen-carpel-stamen-carpelsepal-petal-stamen-carpel56wtpistillata(pi)sepal-sepal-carpel-carpelsepal-petal-stamen-carpelapetala3(ap3)57sepal-petal-stamen-carpelsepal-petal-petal-sepal58The“ABC”model for

38、flower developmentThe ABC genes function in the distinct fields.The A and C genes are mutually exclusive in their expression.ABCAP1,AP2AP3,PIAG59The A genes:ap1 or ap2 mutants should(and do)make carpel-stamen-stamen-carpelap1 or ap2WT60The B genes:ap3 or pi mutants should(and do)make sepal-sepal-car

39、pel-carpelWTap3 or pi61The C genes:ag mutants should(and do)make sepal-petal-petal-sepalWTagMADS-box proteins(MCM1,AG,DEF,SRF)Plant MADS-box proteins belong to two large families:the type I class,which group with the human SRF protein,and the type II class that groups with yeast MEF2ABCE model(A)BC

40、model 66Gametogenesis and FertilizationFlower organ function:67generative cellDiploid pollen mother cells undergo meiosis to produce a tetrad of haploid microspores.Each microspore develops into a pollen grain containing two haploid cells(mitosis I):the generative cell(small)The vegetative cell(larg

41、e)Male gametogenesis68the vegetative cell grows to produce the pollen tubethe generative cell produce 2 sperm cells(mitosis II)69an ovule primordium emerges as a bump on the inner wall (placenta)of the ovarythe megasporocyte undergoes meiosis to produce 4 haploid cells,only one of which(the megaspor

42、e)survives.Female gametogenesis70placental wallFemale gametogenesisthe megaspore undergoes 3 mitotic divisions to produce 8 cells:3 antipodal cells 2 synergid cells 2 central cell nuclei 1 egg cell(EC)71Female gametogenesisplacental wall72Double fertilizationPollens land on the stigma,hydrate,and be

43、gin to germinate the pollen tube73Pollen tubes grow,by tip growth,down through the stigma and style and into the ovary,toward the ovules.The pollen tube navigates to the micropyle and discharges the two sperm cells.74One sperm fertilizes the egg cell to develop into the embryo.the other sperm fertil

44、izes the diploid central cell nucleus to develop into the endosperm.MicropyleEggSynergidsAntipodal cellsCentral cell nucleiSpermsPollen tubeOvuleDouble fertilization75Plant reproductionOvule(1 to many)OvarySilique（长角果）76Fruit developmentThe ovary and other tissue together produce a fruit.Fruit is important for seed dispersal in many speciesMany foods are also called“vegetables”:tomatoes,pea,squashFruit size,texture,and sugar content are determined by genes.Ethylene stimulates fruit ripening.77Life cycle of a flowering plant2n2n2n2n1n2n