C8545 Developmental Biology Lesson 7 Plant Embryogenesis 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  Capron A, Chatfield S, Provart N, Berleth T 2009. Embryogenesis: Pattern Formation from a Single Cell. The Arabidopsis Book. Rockville, MD: American Society of Plant Biologists, doi: 10.1199/tab.0126, http://www.aspb.org/publications/arabidopsis/.  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 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis □ Mechanism of the apical-basal axis formation  female gametophyte prespecification, invariant cell division or positional information?  differential gene expression  auxin gradients formation  the role of auxin signalling □ Roor meristem formation  auxin and hypophysis identity  differential gene expression and root meristem patterning  auxin-cytokinin interaction and the root meristem organization centre formation 4 Outline of Lesson 7 Plant Embryogenesis □ Patterning of the apical embryo pole  generation of cotyledons and shoot apical meristem  proper spacing of lateral organs  adaxial-abaxial axis formation □ Radial embryo patterning  epidermal layer specification  separating vascular and ground tissue 5 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis 6 Hejátko et al., Mol Genet Genomics (2003) Hypofýza Hypophysis Protoderm Protoderm Apical cell-active protein biosynthesis Basal cell-highly vacuolated Horní patro Upper tier Dolní patro Lower tier Anticlinal divisions Capron et al., Arabidopsis Book (2009) SuspenzorEmbryoproper 7 Capron et al., Arabidopsis Book (2009) Apical cell Basal cell Proembryo Four out of eight cells of the embryo proper Octant stageProembryo stage 8 Protoderm Prospective vascular tissue Capron et al., Arabidopsis Book (2009) Dermatogen stage Early globular stage Triangular embryo stage Prospective ground tissue/základní pletivo U/L tier diffrentiation 9 Capron et al., Arabidopsis Book (2009) Heart stage Topedo stage Bended cotyledon stage 10 Capron et al., Arabidopsis Book (2009) Vodivá pletiva Vascular tissue Základní pletivo Ground tissue Děložní lístky Cotyledons SAM RAM Epidermis (from protoderm) Prospective root meristem (from hypophysis) 11 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis □ Mechanism of the apical-basal axis formation  female gametophyte prespecification, invariant cell division or positional information? 12 Capron et al., Arabidopsis Book (2009) Hejátko et al., Mol Genet Genomics (2003) twin Proximal Distal Proximal Distal WT 13 Torres-Ruiz and Jurgens, Development (1994) WT WT fsfs 14 Torres-Ruiz and Jurgens, Development (1994) WT fs 15 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis □ Mechanism of the apical-basal axis formation  female gametophyte prespecification, invariant cell division or positional information?  differential gene expression 16 Capron et al., Arabidopsis Book (2009) Differential expression of WUSCHEL-RELATED HOMEOBOX (WOX) gene family hypophysis 17 Capron et al., Arabidopsis Book (2009), SHORT SUSPENSOR (SSP) interleukin-1 receptor–associated kinase (IRAK)/Pelle-like kinase YODA (YDA) mitogen-activated protein kinase kinase (MAPKK) 18 Bayer et al., Science (2009) SSP mRNA in situ localization SSP-YFP 19 Grossniklaus, Science (2009) 20 Bayer et al., Science (2009) Pro35S:SSP-YFP/WT Pro35S:ssp-YFP/WT Pro35S:SSP-YFP/yda myristoylation-deficient variant 21 Gray and Hetherington, Curr Biol (2004) Bergmann, Curr Opin Plant Biol (2006) SSP Serna, Bioessays (2009) Meristemoid 22 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis □ Mechanism of the apical-basal axis formation  female gametophyte prespecification, invariant cell division or positional information?  differential gene expression  auxin gradients formation 23 Dubova, Hejatko, Friml (2005)Benkova et al., Cell (2003) DR5:GFP Immunodetetcion of IAA 24 Bowman et al., Annu. Rev. Plant. Biol (2008) 25 Bowman et al., Annu. Rev. Plant. Biol (2008) 26 CTRL + NPA CTRL + BFA Friml, Nature (2003) octant stage globular stage Ball-shaped embryo 27 Capron et al., Arabidopsis Book (2009) PIN7 PIN1 Dermatogen stage PIN7 relocalization Bilateral symetry via PIN1 localization 28 WT pin7 Friml et al., Nature (2003) 29 mp mp bdl gn Friml et al., Nature (2003) Richter et al., E J Cell Biol (2010) gnWT gnWT Mutations affecting embryo patterning are associated with changes in the auxin maxima formation Adenosyl ribosylation factor Guanine nucleotide Exchange Factor (ARF GEF), 30 Geldner et al., Cell (2003) GN GN-myc +BFA GNM696L-myc+ BFA 31 Richter et al., E J Cell Biol (2010) Anterograde transport Retrograde transport Trans-Golgi network Multivesicular bodies-late endosome (prevacuolar compartment) Recycling endosome 32 Shin et al., J Biochem (2004) A Adenosyl ribosylation factor Adenosyl ribosylation factor Guanine nucleotide Exchange Factor (ARF GEF), GTPase-activating protein 33 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis □ Mechanism of the apical-basal axis formation  female gametophyte prespecification, invariant cell division or positional information?  differential gene expression  auxin gradients formation  the role of auxin signalling 34 MP/ARF5 BDL/IAA12 Capron et al., Arabidopsis Book (2009) Auxin signalling and its role in the embryo patterning 35 Capron et al., Arabidopsis Book (2009) Szemenyei et al., Science (2008) WT tp l bdl bdl, tpl Non-permisive conditionsPermisive conditions Undifferentiated peg Auxin maxima in lens shaped cell TPL auxin shoot identity auxin root identity BDL, MP BDL, MP TPL Root-specific interaction of TPL with bdl? 36 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis □ Mechanism of the apical-basal axis formation  female gametophyte prespecification, invariant cell division or positional information?  differential gene expression  auxin gradients formation  the role of auxin signalling □ Root meristem formation  auxin and hypophysis identity 37 Sheres et al., Development (1994) Root apical meristem develops from the LT descendants 38 Lens shaped cell Capron et al., Arabidopsis Book (2009) Klidové centrum Quiscent centre Organizational centre for the RAM formation 39 Lens shaped cell Hypophysis Auxin flow from the UT Capron et al., Arabidopsis Book (2009) auxin TOM TF BDL, MP Globular stage Late globular-early triangular embryo stage Weijers et al., Dev Cell (2006) 40 Capron et al., Arabidopsis Book (2009) Stem cell niche Stem cell-maintenance signal Endodermis-inducing signal Stabilization of tissue identity signal 41 Capron et al., Arabidopsis Book (2009) auxin response maximum displaced 42 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis □ Mechanism of the apical-basal axis formation  female gametophyte prespecification, invariant cell division or positional information?  differential gene expression  auxin gradients formation  the role of auxin signalling □ Roor meristem formation  auxin and hypophysis identity  differential gene expression and root meristem patterning 43 Capron et al., Arabidopsis Book (2009) Auxin-dependent and auxin-independent differential gene expression patterns root meristem Auxin-dependent Auxin-independent root-specific gene expresion 44 Outline of Lesson 7 Plant Embryogenesis □ Overview of the embryo formation in Arabidopsis □ Mechanism of the apical-basal axis formation  invariant cell division or positional information?  differential gene expression  auxin gradients formation  the role of auxin signalling □ Roor meristem formation  auxin and hypophysis identity  differential gene expression and root meristem patterning  auxin-cytokinin interaction and the root meristem organization centre formation 45 Signal Transduction via TCS 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 Recent Model of the CK Signaling via TCS Pathway D’Agostino et al., Plant Physiol, 2000 CK primary response genes - Type-A ARRs expression 46 Muller and Sheen., Nature (2008) 47 Muller and Sheen., Nature (2008) arr15/arr7arr15/ARR7 48 Outline of Lesson 7 Plant Embryogenesis □ Patterning of the apical pole of the plant embryo  generation of cotyledons and shoot apical meristem 49 Capron et al., Arabidopsis Book (2009) WUS expression domain SAM specification 50 Capron et al., Arabidopsis Book (2009) 51 CUCSTM cotyledonsCapron et al., Arabidopsis Book (2009) Gene interactions during apical embryo pole patterning Specification and maintenance of SAM Proper spacing of SAM and cotyledons Lateral organ differentiation vs. meristem maintenance AS1 52 Outline of Lesson 7 Plant Embryogenesis □ Patterning of the apical pole of the plant embryo  generation of cotyledons and shoot apical meristem  proper spacing of lateral organs 53 Capron et al., Arabidopsis Book (2009) Auxin maxima are involved in lateral organ formation and acquiring of billateral symmetry 54 Capron et al., Arabidopsis Book (2009) Concerted action of auxin transporters (influx and efflux carriers)PINs AUX1 and LAX1 55 Outline of Lesson 7 Plant Embryogenesis □ Patterning of the apical pole of the plant embryo  generation of cotyledons and shoot apical meristem  proper spacing of lateral organs  adaxial-abaxial axis formation 56 P3 P2 P1 I1 I2 I3 P3 P2 P1 I1 I2 I3 Incision in the meristem developing primordium radial organ formation abaxial leaf side adaxial leaf sideCapron et al., Arabidopsis Book (2009) SAM-derived signals induce adaxial-abaxial diversification SAM-inducing positive feedback from the adaxial pole 57 Capron et al., Arabidopsis Book (2009) Specificity in gene expression is involved in the adaxial-abaxial patterning 58 Bowman et al., Annu. Rev. Plant. Biol (2008) 59 Outline of Lesson 7 Plant Embryogenesis □ Patterning of the apical pole of the plant embryo  generation of cotyledons and shoot apical meristem  proper spacing of lateral organs  adaxial-abaxial axis formation □ Radial embryo patterning  epidermal layer specification 60 Capron et al., Arabidopsis Book (2009) Epidermal layer specification Single morphogen model “Ouside-in” model knolle and keulle cytokinesis mutants (incomplete CW) ectopic expression of epidermal markers 61 ProATML1:NLS-3xeGFP MERISTEM LAYER1 (AtML1) and PROTODERMAL FACTOR 1 and 2 62 Outline of Lesson 7 Plant Embryogenesis □ Patterning of the apical pole of the plant embryo  generation of cotyledons and shoot apical meristem  proper spacing of lateral organs  adaxial-abaxial axis formation □ Radial embryo patterning  epidermal layer specification  separating vascular and ground tissue 63 Separation of vascular and ground tissue Cell divisons predominantly along the apical-basal axis Early globular stage 64 endodermis cortex epidermis 65 ProSCR:SHR WT SHR SCR 66 Key Concepts Plant Embryogenesis □ Similarly to animals, both embryonic and extraembryonic tissue forms during plant embryogenesis □ In plant embryogenesis, positional information rather than invariant cell division is decisive for the proper embryo patterning □ Auxin gradient formation provides positional information that together with differential gene expression directs downstream developmental events during plant embryogenesis □ Auxin transport machinery and auxin signalling are critical for the proper embryo development □ Interaction of auxin with other growth regulators, e.g. cytokinins emerges as a crucial regulatory factor for many developmental processes during plant embryo formation □ Gene and protein interactions allow formation of distinct cell and tissue spatial patterns and allow proper organogenesis 67 Discussion