首页 > 分享 > 高级植物生理学课件第七章植物的生殖生理.ppt

高级植物生理学课件第七章植物的生殖生理.ppt

花匠小妙招
2025-09-26 15:40

1、单击此处添加副标题内容高级植物生理学课件第七章植物的生殖生理单击此处输入你的正文，文字是您思想的提炼，为了最终演示发布的良好效果，请尽量言简意赅的阐述观点。2Plant ReproductionZichao Mao 3Life cycle of plant 4 Transition to reproduction Flower organ development Gametogenesis and fertilizationPlant Reproduction5Transition to reproductionVegetative phaseReproductive phaseInflore

2、scenceFlower6Production of flowers involves two transitions in ArabidopsisSC:stem cellP:organ primordiaSe:sepalConvert SAM（Shoot Apical Meristem)to inflorescence meristem(infinite,making lateral organs)2.Convert inflorescence meristem to floral meristem(terminal,flowers)7Factors regulating the trans

3、itionsVegetative meristemInflorescence meristemFloral meristemGenes(flowering-time genes and floral identity genes)Light(photoperiod)The biological clockTemperature Hormones 8affecting the transition of vegetative growth to reproductive growthWTemf2Flowering-time genesemf1embryonic flower9affecting

4、formation of inflorescence and floral meristemsFloral identity genesInflorescence(from Inflorescence meristem)Flower(from Floral meristem)10terminal flower 1(tfl1):Convert the inflorescence meristem to the flower meristem.leafy(lfy):produce more inflorescences,delayed floweringMutations in floral id

5、entity genestfl1 FUNCTION Controls inflorescence meristem identity and is required 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 pho

6、sphorylated ligands by interfering with kinases and their effectors Expressed below 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;L

7、FY,FUNCTIONS IN:chromatin DNA binding,transcription factor activity,sequence-specific 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,e

8、mbryo,flower,seed;EXPRESSED DURING:7 growth stages;13Factors regulating the transition to reproductionVegetative meristemInflorescence meristemFloral meristemEMFTF1LFY14Garner and Allard(1920s)The discovery of photoperiodismSoybeans(Glycine max)planted over a three-month period all flowered about th

9、e same time15Many more experiments were followed:Eliminate a variety of environmental 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 16V

10、aries according to the latitude and seasonal changes.Photoperiod17Critical daylengthCriticalDaylength(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.18Plants are induced to flower by different photoperio

11、dsshort day(SD):plants are stimulated to flower when the length of day falls below 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 numbe

12、r of short days are preceded by a certain number of long days.Short-long-day:flowering 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

13、 in the spring or early summer are known as long-day(LD)plants.Short-day(SD)plants flower in the late summer or autumn in response to shortening days and lengthening nights 20Do plants really measure the length of the daylength?21 Xanthium flowers when the dark period exceeds 8.5 hours.Hamner and Bo

14、nner(1938):Xanthium strumarium(苍耳）,a SD plant with CD=15.5 hours Short interruption 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.22Similar results were obtained with other SD plants.For LD plantsA longer dark

15、period inhibits flowering.Light break induces flowering.23What tissues/organs perceive photoperiod?24Exp.1:The leaf or apex of Perilla（紫苏）(a short day plant)was exposed to different daylength.25Exp.2:Grafting experiment with Perilla26 the flowering signal is generated in the leaf the signal goes one

16、 way:from the leaf to the apex Grafting transmittableThe flowering signal:florigen?vegetative 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

17、FT gene is expressed in leaves,and the protein travels to the meristem where it interacts 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 po

18、plarThe role of phytochrome in de-etiolation responsePhytochrome:a molecular switching mechanismThe effect of light on the biological clockwPhytoperiodism and control of floweringPhytoperiodism and control of floweringwShort-day plant:required a light period shorter than Short-day plant:required a l

19、ight period shorter than a critical length to flowera critical length to flowerwlong-day 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 pla

20、nt:unaffected by photoperiod and flower when reaching a certain stage of maturityflower when reaching a certain stage of maturitywVernalization:use of pretreatment with cold to Vernalization:use of pretreatment with cold to induce floweringinduce flowering33The Arabidopsis biological clockThe centra

21、l oscillator:CCA1,LHY,and TOC1(these are transcription factors)and other proteins34 Present in plants,animals,fungi,and some photosynthetic bacteria An 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

22、 clockTemperatureBiological clocks andcircadian rhythms37The Arabidopsis biological clock CCA1 and LHY are expressed during the day and together repress expression of TOC1 during the day TOC1 is expressed at night and is required for activation of CCA1 and LHY1,beginning just before morning38Lack of

23、 the nyctinastic movement:diurnal rise and fall of leavesAltered flowering time in some mutantscca1:early floweringlhy:early floweringtoc1:early floweringSome other clock mutants can be late flowering Mutations in the clock genes39Temperature:VernalizationVernalization:low temperature treatment can

24、promote flowering in some plants.The vernalization-effective temperature and duration of low 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

25、 treatment Plants have evolved many systems to sense their environment and to modify their 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 adap

26、tive trait that helps prevent flowering before winter and permits flowering in the favorable 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.I

27、n Arabidopsis,vernalization involves the recruitment of chromatin-modifying complexes to a clade of flowering repressors that are silenced epigenetically via histone modifications.vernalization42 Can be induced quickly Increases plant resistance to freezing stress Does not affect flowering time.Cold

28、 acclimationVenalization in cerealsMachanism of Vernalization Vernalization-mediated changes in 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

29、(H3K4triMe and H3K36triMe),a SWR1-like complex,which deposits a histone 2A variant in the nucleosomes 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 Repres

30、sion Complex 2 and some degree of lysine 27 methylation of histone 3(H3K27triMea repressive modification)(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 meth

31、ylation of histone 3 increases,and repressors such as LIKE HETEROCHROMATIN PROTEIN 1(LHP1)assemble 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 methyltransfera

32、se(HMTase)increases.(d)Eventually,a mitotically stable state of repression that no longer requires 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

33、VRN1 to maintain a repressive state.As the FLC locus passes to the next generation,the active chromatin state represented in(a)is re-established 48Hormone GA regulates flowering timeGA1:an enzyme involved in GA biosynthesisga1:In addition to the dwarf phenotype,the mutant flowers late under LD condi

34、tions and does not flower under SD conditions.GA treatment promotes flowering time.49Flower development in ArabidopsisVegetative meristemInflorescence meristemFloral meristemFlower:sepals,petals,stamens,and carpelsTransition to reproduction:Genes&other factorsFlower organ development:Organ identity

35、genes One of the early successes of the application of molecular genetics to study plant development 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

36、 list of genes has been defined and,great progress has been made in understanding how they are regulated,how they act together,what they do and how they have contributed to the evolution of the flower in its varied forms.52Flower organs petal stamen carpel sepal53The flower is generated from the flo

37、ral meristem the floral meristem54Produced in 4 concentric whorls with the same ordersepal(whorl 1)stamen(whorl 3)petal(whorl 2)carpel(whorl 4)Flower organs ABC model 56(the ap1 mutant is similar)stamen-carpel-stamen-carpelsepal-petal-stamen-carpel57wtpistillata(pi)sepal-sepal-carpel-carpelsepal-pet

38、al-stamen-carpelapetala3(ap3)58sepal-petal-stamen-carpelsepal-petal-petal-sepalQuickTime and aTIFF(LZW)decompressorare needed to see this picture.59The“ABC”model for flower development The ABC genes function in the distinct fields.The A and C genes are mutually exclusive in their expression.ABCAP1,A

39、P2AP3,PIAG60The A genes:ap1 or ap2 mutants should(and do)make carpel-stamen-stamen-carpelap1 or ap2WT61The B genes:ap3 or pi mutants should(and do)make sepal-sepal-carpel-carpelWTap3 or pi62The C genes:ag mutants should(and do)make sepal-petal-petal-sepalWTagMADS-box proteins(MCM1,AG,DEF,SRF)Plant M

40、ADS-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 model 67Gametogenesis and FertilizationFlower organ function:68generative cellDiploid pollen mother cells undergo meiosis to produce

41、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(large)Male gametogenesis69 the vegetative cell grows to produce the pollen tube the generative cell produce 2 sperm cells(mitosis II)70an

42、 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 megaspore)survives.Female gametogenesis71placental wallFemale gametogenesisthe megaspore undergoes 3 mitotic divisions to produce 8 cells:3

43、 antipodal cells 2 synergid cells 2 central cell nuclei 1 egg cell(EC)72Female gametogenesisplacental wall73Double fertilizationPollens land on the stigma,hydrate,and begin to germinate the pollen tube74Pollen tubes grow,by tip growth,down through the stigma and style and into the ovary,toward the o

44、vules.The pollen tube navigates to the micropyle and discharges the two sperm cells.75One sperm fertilizes the egg cell to develop into the embryo.the other sperm fertilizes the diploid central cell nucleus to develop into the endosperm.MicropyleEggSynergidsAntipodal cellsCentral cell nucleiSpermsPo

45、llen tubeOvuleDouble fertilization76Plant reproductionOvule(1 to many)OvarySilique（长角果）77Fruit development The ovary and other tissue together produce a fruit.Fruit is important for seed dispersal in many species Many foods are also called“vegetables”:tomatoes,pea,squash Fruit size,texture,and sugar content are determined by genes.Ethylene stimulates fruit ripening.78Life cycle of a flowering plant2n2n2n2n1n2n学习交流共同提高感谢观赏