C8545 Developmental Biology Lesson 6 Plant Reproduction Jan Hejátko Functional Genomics and Proteomics of Plants CEITEC and National Centre for the Biomolecular Research, Faculty of Science Masaryk University, Brno hejatko@sci.muni.cz, www.ceitec.eu 2 Literature  Fred H. Wilt and Sarah Hake, Principles of Developmental Biology (W.W. Norton & Company, New York, London, 2004)  Scott F. Gilbert, Developmental Biology, eighth edition (Sinauer Associates, Inc., Publishers Sunderland, Massachusetts, USA, 2006)  Dubová J., Hejátko J., Friml J. (2005) Reproduction of Plants, in Encyclopedia of Molecular Cell Biology and Molecular Medicine (ed, R. A. Meyers), pp. 249 – 295. Wiley-VCH, Weinheim, Germany  Selected original papers in scientific journals 3 □ Sexual and asexual plant reproduction □ Plant life cycle □ Initiation of flowering □ Determination of floral organ identity □ Microgametogenesis □ Megagametogenesis  Female gametophyte patterning □ Pollen tube growth, guidance and fertilization □ Endosperm and seed formation Outline of Lesson 6 Plant Reproduction 4 □ Sexual and asexual plant reproduction Outline of Lesson 6 Plant Reproduction 5 Nucellus Degenerating mother megaspore cell Asexual Plant Reproduction 6 □ Sexual and asexual plant reproduction □ Plant life cycle Outline of Lesson 6 Plant Reproduction 7 Plant Life Cycle 8 Dubova, Hejatko, Friml (2005) Plant Life Cycle Mosses 9 Dubova, Hejatko, Friml (2005) Plant Life Cycle Ferns prothalium 10 Plant Life Cycle Angiosperms 11 Plant Life Cycle Angiosperms 12 □ Sexual and asexual plant reproduction □ Plant life cycle □ Initiation of flowering Outline of Lesson 6 Plant Reproduction 13 Listeny Uzavřené květenství (monotelické) Determinate inflorescence Listy Otevřené květenství (polytelické) Indeterminate inflorescence Antirrhinum Arabidopsis Flowering 14 Esau, 1977 WUS WOX5 Lateral meristems Plant Grow thanks to Meristems Apical meristems Meristem Types 15 rosette leaves vegetative growth phase produced by SAM generative growth phase inflorescence flowers cauline leaves (bracts) branches produced by FMs • LFY • AP1 produced by IM • TFL1 meristem identity genes flowering time genes floral organ identity genes floral shoot Changes in Meristem Identity 16 Initiation of Flowering 17 WT id1 id1 Lata (klásků) Tassel Palice Ear In situ hybridization with INDETERMINATE (ID1) mRNA… ….in leaves ….and SAM KN1 Initiation of Flowering 18 photoperiod/light quality vernalization autonomous hormones Dubova, Hejatko, Friml (2005) Flowering Control 19 Pro35S:LFYWT Flowering Control 20 Dubova, Hejatko, Friml (2005) I. Inflorescence meristem formation (switch from vegetative to reproductive growth) II. Floral meristem identity acquisition (LFY, AP1) III. Activation of floral organ identity genes (whorl-specific) IV. Activation of floral organ building genes Flowering Control 21 Flower Development 22 Flower primordia (buds) Okvětní lístky Sepals Dlouhé tyčinky Long stamens Korunní lístky Petals Smyth et al., Plant Cell (1990) Floral Organ Formation 23 Okvětní lístky Sepals Dlouhé tyčinky Long stamensKorunní lístky Petals Krátké tyčinky Short stamens Krátké tyčinky Short stamens Pestík Gynoeceum (pistil) Smyth et al., Plant Cell (1990) Floral Organ Formation 24 Smyth et al., Plant Cell (1990) Okvětní lístky Sepals Korunní lístky Petals Pestík Gynoeceum (pistil) Blizna Stigma Floral Organ Formation 25 □ Sexual and asexual plant reproduction □ Plant life cycle □ Initiation of flowering □ Determination of floral organ identity Outline of Lesson 6 Plant Reproduction 26 Floral Organ Identity 27 MADS-box genes •MCM1 (yeast) •AGAMOUS (Arabidopsis), •DEFICIENS (Antirrhinum), •SERUM RESPONSIBLE FACTOR (human). ABC Model 28 Author of ABC model, professor Elliot Meyerowitz (middle) during his visit of MU campus in Mar 2008 ABC Model 29 □ Sexual and asexual plant reproduction □ Plant life cycle □ Initiation of flowering □ Determination of floral organ identity □ Microgametogenesis Outline of Lesson 6 Plant Reproduction 30 microsporangia megasporangia Microgametogenesis 31 Dubova, Hejatko, Friml (2005) Sperm cells Pylová pouzdra (váčky) Microsporangia (locules) Microgametogenesis Archespora Archesporial cell NZZ/SPL AG Callose (β-1,3-glucan) 32 Microgametogenesis 33 □ Sexual and asexual plant reproduction □ Plant life cycle □ Initiation of flowering □ Determination of floral organ identity □ Microgametogenesis □ Megagametogenesis Outline 34 Placenta Replum Megagametogenesis 35 MMC Vascular tissue Inner integument Outer integument Prospective functional megaspore Prospective Nucelus Prospective Chalaza Prospective Funiculus Micropyle Chalaza Funiculus Dubova, Hejatko, Friml (2005) NZZ/SPL NZZ/SPL+ANT + WUS Archesporialcell differentiation Megagametogenesis 36 Dubova, Hejatko, Friml (2005) Megagametogenesis 37 Dubova, Hejatko, Friml (2005) Megagametogenesis 38 Identification of CKI1 via Activation Mutagenesis  CKI1 overexpression mimics cytokinin response Kakimoto, Science, 1996 NO hormones tZ ctrl1 ctrl2Plasmid Rescue Pro35S::CK1 39 Signal Transduction via MSP NUCLEUS CYTOKININ PM AHK sensor histidine kinases • AHK2 • AHK3 • CRE1/AHK4/WOL REGULATION OF TRANSCRIPTION INTERACTION WITH EFFECTOR PROTEINS HPt Proteins • AHP1-6 Response Regulators • ARR1-24 40 CKI1/cki1-i CKI1/CKI1 CKI1 Controls Megagametogenesis 41 cki1-i reveals non-Mendelian inheritance ♂ ♀ P CKI1/cki1-i F1 Anticipated: CKI1 cki1-i CKI1 cki1-i CKI1/CKI1 CKI1/cki1-i CKI1/cki1-i cki1-i/cki1-i 1 CKI1 : 2 CKI1/cki1-i : 1 cki1-i Observed: 1 CKI1 : 1 CKI1/cki1-i 42 A. ♂ wt x ♀ CKI1/cki1-i B. ♂ CKI1/cki1-i x ♀ wt C. ♂ wt x ♀ CKI1/cki1-i D. ♀ wt x ♂ CKI1/cki1-i CKI1 specific primers (PCR positive control) cki1-i specific primers CKI1 Controls Megagametogenesis 43 FG 0 FG 1 FG 2 FG 3 FG 4 MMC Hejátko et al., Mol Genet Genomics (2003) CKI1 Controls Megagametogenesis 44 cki1-iCKI1 late FG5 24 HAE Hejátko et al., Mol Genet Genomics (2003) CKI1 Controls Megagametogenesis 45 FG6 24 HAE CKI1 Controls Megagametogenesis 46 48 HAEFG7 CKI1 Controls Megagametogenesis 47 FG0-FG1 FG3-FG4 FG4-FG5 FG7 Hejátko et al., Mol Genet Genomics (2003) CKI1 Activity during Megagametogenesis 48 □ Sexual and asexual plant reproduction □ Plant life cycle □ Initiation of flowering □ Determination of floral organ identity □ Microgametogenesis □ Megagametogenesis  Female gametophyte patterning Outline of Lesson 6 Plant Reproduction 49 Pagnussat et al., Science (2009) Female Gametophyte Patterning 50 Pagnussat et al., Science (2009) Female Gametophyte Patterning 51 Pagnussat et al., Science (2009) YUC1::GUS YUC2::GUS FG1 FG3 FG4 Female Gametophyte Patterning 52 Pagnussat et al., Science (2009) Female Gametophyte Patterning 53 Pagnussat et al., Science (2009) Female Gametophyte Patterning 54 Sundaressan and Alandete-Saez, Development (2010) Female Gametophyte Patterning 55 □ Sexual and asexual plant reproduction □ Plant life cycle □ Initiation of flowering □ Determination of floral organ identity □ Microgametogenesis □ Megagametogenesis  Female gametophyte patterning □ Pollen tube growth, guidance and fertilization Outline of Lesson 6 Plant Reproduction 56 Suzuki, Plant and Cell Physiol (2009) Pollination and Fertilization 57 Kost., Trends in Plant Science (2008) ↑ GTP→↑pollen tube growth RopGTPases interact with Ca2+ gradient Pollen Tube Growth 58 Marton and Dresselhaus., Plant Sex Reprod (2007) Chemotaxis Chemo- and Thermotaxis Chemotaxis sea urchin mammals plants Chemotaxis and Fertilization 59 Okuda et al., Natture (2009) Protruding nucellus of Torenia ovules LURE1 and LURE2 (CRPs) → RLKs → pollen tube and synergid behavior LURE1 Filiform apparatus Pollen Tube Guidance 60 Marton etal., Science (2005) Zm EGG APARATUS1 mRNA ProZmEA1:GUS Pollen Tube Guidance 61 Marton etal., Science (2005) Pollen tube Pollen Tube Guidance 62 Berger etal., Trends in Plant Science (2008) Receptive synergid •cytoskeleton reorganization •Ca2+ acumulation •Organelles and plasmamembrane degeneration Fertilization 63 Dumas and Rogowsky., C. R. Biologies (2008) Dnase-mediated degradation of synergid and vegetative cell nuclei Actin-corona-mediated nuclei movement Karyogamy (double) and Ca2+ release Fertilization 64 □ Sexual and asexual plant reproduction □ Plant life cycle □ Initiation of flowering □ Determination of floral organ identity □ Microgametogenesis □ Megagametogenesis  Female gametophyte patterning □ Pollen tube growth, guidance and fertilization □ Endosperm and seed formation Outline of Lesson 6 Plant Reproduction 65 Dubova, Hejatko, Friml (2005) Central vacuole Endoreduplication Mycropylar endosperm Peripheral endosperm Chalazal endosperm Endosperm Formation 66 Dubova, Hejatko, Friml (2005) Radial microtubule system and alveoli formationCellularization Chalazal cyst Aleurone Endosperm Formation 67 12 HAP 24 HAP 48 HAP 72 HAP ♀ wt x ♂ CKI1prom::uidA Hejátko et al., Mol Genet Genomics (2003) CKI1 Activity in Endosperm 68 □ In plants, gametophytic and sporophytic portion (“generation”) of the life cycle could be distinguished □ Initiation of flowering integrates multiple inputs (light quality/photoperiod, vernalization, autonomous and hormonal signals) □ Several developmental switches resulting into acquisition of floral meristem and floral organ identity take place during onset of flowering. These switches are under control of specific genes that mutually interact □ In angiosperms, the gametophyte is reduced to three-celled pollen tube (male gametophyte) and mostly seven-celled female gametophyte (embryo sac). Auxin gradient determines acquisition of cell identity during embryo sac development □ Pollen tube growth is complex process associated with large amount of cell material deposition. Pollen tube guidance is mediated by specific molecules allowing synergid-cell mediated chemotaxis. □ Expression of maternal and paternal genes is tightly regulated during seed development. Key Concepts 69 Discussion