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Towards multicellularity

Towards multicellularity. Four elements to make a multicelluar organism. Apoptosis. Information exchange. External s ecretion. Colonial organization. Bacteria. Paenibacillus forms colonies moves on hard s urfaces through jointly secreted lubricants communicates with other cells

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Towards multicellularity

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  1. Towards multicellularity Four elements to make a multicelluar organism Apoptosis Informationexchange External secretion Colonialorganization Bacteria • Paenibacillus • forms colonies • moves on hard surfaces through jointly secreted lubricants • communicates with other cells • no apoptosis • no real cell differentiation Paenibacillus dendritiformis • Myxobacteria • form colonies of millions of cells • Some have coordinated movements • form biofilms • largest bacterial genomes (9 - 12 kB) • some produce fruiting bodies for the release of spores • no apoptosis • rudimentary cell differentiation Myxococcus xanthus Why did Bacteria not evolve true multicellularity? Maybe their limits in genome size do not allow for higher order differentiation.

  2. Nanowires and electrical signalling Geobacter sulfurreducens Microbial electrical cell-cell communication via nanowires may be widespread in nature.

  3. Four elements to make a multicelluar organism Apoptosis Information exchange External secretion Colonial organization Stigmergy:indirect signalling by secretion Cell differentiation Vascular plants Metazoa Early differentiation of germ line High degree of cell differentiation Real tissues Organs Central coordination Specialized cells reproduce High degree of cell differentiation Real tissues Organs No central coordination Fungi Specialized cells reproduce Cell differentiation No real tissues No organs Multicellularity probably monophyletic Brown algae Slime moulds Chlorophytes Specialized cells reproduce Cell differentiation Real tissues No organs Facultative multicellularity Limited cell differentiation No real tissues No organs Facultative multicellularity Rudimentary cell differentiation No real tissues No organs Multiple origin of multicellularity in each of these groups

  4. The multi-taxon genome initiative Single celled parasites of marine pulmonate snails Some species form colonies Pseudo-multicellular colonies Capsaspora Choanoflagellata True multicellularity Metazoa Ichthyospora Parasitic Nematostella Sphaeroforma arctica Free living Single celled marine heterotroph Ministeria Free living Fungi Chorallochytrium Nuclearia Parasitic Apusozoa Single celled aquatic heterotroph Single celled free living marine heterotroph Amoebozoa Single celled terrestrial oraquatic bacteriophages Corallochytriumlimacisporum

  5. Mesoproterozoicum 1600-1000 Tonian 1000-850 Ordovician490-440 Silurian 440-410 Devonian 410-355 Carboniferous 355-290 First Glomeromycota fossils First lichens Lecanoromycetes lichenized terrestrial Ascomycota(Saccharomyces cerevisiae) Dicaria Basidiomycota Ektomycorrhiza Glomeromycota Arbuscular mycorrhiza Zygomycota Phycomyces Multiple loss of flagellum Saprotroph / mutualists Chytridium Chytridiomycota Fungi Microsporidia Arthropod pathogen Nuclearia simplex Amphiacantha Metazoa Opistho-konta Nuclearia Choanoflagellata phagotroph Mycetozoa s.str. Unikonta terrestrial Oomycota Plant pathogen (Chromista) Bikonta Plantae Phytophora infestans

  6. The MAGI genes Guanylate kinases regulate tight tissue junctions PDZ signal PDZ signal ww guk Generalized Metazoa Zebra fish Ichthyospora Single cell organisms Parasites of marine fish, birds and mammals Some species form pseudo- multicellular colonies Ichthyospora

  7. A major invention: Metameria Christiane Nüsslein-Volhard (1942-) Walter Jacob Gehring (1939-) All animals share a common gene family, the homeobox family, that controls metameric and embryonal development. Extended Hox NKL Para Hox EHG box Early Vertebrates EHG box Proto Hox Proto NKL Early arthropods Cnidaria Early Metameria Arche Hox Trichoplax adhaerens In sponges and Ctenophora Hox genes haven’t been detected yet.

  8. The evolution of Hox genes Homeotic genes: MADS-box Plants Homeotic genes Convergent evolution of genes that regulate ontogenetic development Fungi Metazoa Placozoa Cnidaria Eleutheria dichotoma,Photo from Jacob and Schierwater 2007, Plos One 2: e694. Metameria Homeotic genes: Hox-genes Inactivation of Cnox 3 in the hydrozoan Eleutheria dichotoma produces multiple heads, for instance head duplication and therefore a bilaterian pattern From: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/H/HomeoboxGenes.html

  9. From Tonian to modern times Ediacaran 630Warmer periodinterrupted by local ice ages Dickinsonia Cyclomedusa Tribrachidium Parvancorina Cryogenian 850 Rodinia breaks up. Largest glaciations (snowball earth) ? Biotracers of Porifera Spriggina floundersi Charniodiscus Tonian 1000 Super-continent Rodinia Metazoa Meso-protero-zoicum 1600-1000 Parmia Horodyksia Maybe a homonomous segmented metazoan Maybe a colonial benthic two tissued metazoan ? Photos from Fedonkin 2003

  10. Cambrium 540Warmer period Kimberella, Mollusca: like Chiton Spriggina Arthropoda: Canadia, Annelida Rangeomorpha were fractal organisms developing through simple branching patterns (like Fungi) White sea and Nama assemblages 560Warmer period Shallow water mobile animals related to modern taxa Avalon assemblages 580Warmer period Increase in atmospheric O2 level Charnia Aspidella Tateana Middle Ediacaran 600Local ice ages Advanced Rangeomorpha and simpler Erniettomorpha Probably not related to any modern taxon Immobile, deep-water filter feeders No mouth or gut, no reproductive organs Early Ediacaran 630Warmer period Acri-tarch An early embryo

  11. Mesoproterozoicum 1600-1000 Tonian 1000-850 Cryogenian 850-680 Ediacaran 680-540 Cambrian 540-490 Ambulacraria (Hemichordata, Echinodermata) Blastoporus becomes anus Metameria, Coelom Deuterostomia Chordata No anusNo coelom Xenoturbellida „Bilateria” Ecdysozoa Cycloneuralia(Nematoda, Priapulida) Ecto-, Entoderm Upper and lower side Gastrula, Muscle cells MetameriaPseudocoelom Onychophora Mesoderm Arthropoda Protostomia Lophotrochozoa No anus Plathelminthes s. str. Pseudocoelom Gnathifera Mollusca Metameria, Coelom Annelida s. l. Lophophorata No anus Acoela Nervous cells, Statocyst Pseudocoelom, Anus, Metameria Chaetognatha Multicellularity, Hox box Choanocytes Cnidaria Paraphyletic Cnidocytes, Rhopalia Ctenophora Multiple bilaterality Porifera Paraphyletic Placozoa Choanoflagellata

  12. A functional model of metazoan evolution Information exchange via neurotransmitters Ectoderm Placozoa Mesogloa Trichoplax Ciliate entoderm Porifera Nervous cells A hypothetical creeping animal of Gastrula organization Statocyst Cnidaria Ctenophora Acoela Xeno-turbel-lida Ecdysozoa Lophotrochozoa Deuterostomia s. str.

  13. The molecular evidence Cryogenian 850-630 Ediacaran 630-540 Mass extinction Cambrian 540-490 Ordovician490-440 Silurian440-410 Isopoda Malacostraca Panarthropoda(Tetraconata) Maxillopoda Branchiopoda Tardigrada Hexapoda Cephalocarida Xenocarida Mandibulata Remipedia Pancrustacea Podocopa Ostra-coda Myodocopa Chilopoda „Myriapoda” Diplopoda Pycnogonida Chelicerata Xiphosura, Arachnida Trilobites Beckwithia typa Aglaspida Onychophora Aysheaia

  14. The Cambrian explosion Cambrian 540-490 During the Cambrian atmospheric oxygen concentration increased to a level to allow for the development of hard skeletons. Probably all today’s phyla were already present. First complicated food webs including higher predators appeared. This might have caused the disappearance of the Ediacaran fauna. Waptia, Chelicerata? An early predator Burgessochaeta, Polychaeta An early predator Ottoia, PriapulidaAn early predator Pikaia, Chordata Olenoides serratus, Trilobites Chmatocrinus, CrinoideaThe earliest deuterostomes

  15. Ordovician 490-440 Silurian 440-410 Warm shallow seas Ice ageMass extinction Warm greenhouse phase (high CO2 level) First Cephalopoda (Nautiloids) and Bivalvia. Rise of Brachiopoda and Bryozoa. First primitive terrestrial fungi, vascular plants and animals (millipedes, arachnids) Eurypterus remipes, Chelicerata Trilobites Arthropoda Bryozoa Cooksonia gradeland plants Cephalopoda Conodonts Birkenia, Agnatha

  16. Cambrian 540-490 Ordovician490-440 Silurian 440-410 Devonian 410-355 Molecular data put the divergence of Bryophytes and Tracheophytes to the end of the Proterozoic (540 to 700 mya). Seed plants Pterydophyta Tracheophytes First land plants ? Sphenopsida Psilophyton Isoetales Embryophytes Lycopodiaceae Drepanophycales Parafunaria sinensis Aglaophyton Rhynia Bryophyta Marchantiopsida Charophytes ? Lunularia cruciata Chara

  17. Devonian 410-355 Rather warm, zoned climate Rather warm, zoned climate Southern glaciation, mass extinction Kampecaris forfarensis, Myriapoda Stomata of Rhynia Pterychthyodes, Placoderna Niedźwiedzki et al. 2010) Moresnetia zalesskyi

  18. Carboniferous 355-300 Warm and wet climateHigh oxygen concentration Ice ageMass extinction Delitzshala bitterfeldensis Equisetum Breyeria harlemensis Paleodictyoptera Lepidodendron source of today’s coal Homoptera Euproops rotundatus Xiphosura

  19. Carboniferous 355-300 Warm and wet climateHigh oxygen concentration Ice ageMass extinction Temporal fenestra Diapsid reptiles Anapsid reptiles Synapsid reptiles Homodont Homoodont Heterodont Hylonomusa first primitive Anapsid Petrolacosaurusfirst primitive Diapsid heterodont Archeothyrisfirst primitive Synapsid

  20. Carboniferous 355-290 Permian 290-250 Trias 250-205 Jurassic 205-140 Cretaceous 140-65 Sarco-pterygia Testudines ? Anapsida Mesosauria Euryapsida Lepidosauromorpha Rhyncho-cephalida Anapsid cranion Amnion Squamates Diapsid cranion Pterosauria Dinosauria Aves Crocodylia Archosauromorpha ? Testudines ? Pelycosauria Synapsid cranion Therapsida Mammalia

  21. Permian 300-250 Ice ageMass extinction Warmer and arid Arid Mass extinction Anapsid reptiles Mesosaurus, Permian primitive anapsid aquatic reptile Milleretta, Permian primitive anapsid terrestrial reptile

  22. Permian 300-250 Ice ageMass extinction Warmer and arid Arid Mass extinction Synapsid reptiles Pelycosaur → Therapsida → Theriodontia (mammal like) Dimetrodon, Permian primitive synapsid Pelycosaur Proburnetia, Permian primitive synapsid Therapsid Annatherapsidus petri, Permian synapsid Theriodont Mammal like teeth

  23. Permian 300-250 Ice ageMass extinction Warmer and arid Arid Mass extinction Acrodont and pleurodont dentition Diapsid reptiles LepidosauromorphaSquamata, Tuatara Tuatara, Lepidosauria Ichthyosauria Thermoreg-ulating body cover Ichthyosaurus, Lepidosauria ArchosauromorphaPterosauria, Dinosauria Crocodylomorpha Thecodont dentition Endothermy? Scale derived thermoregulating body cover? Pterodactylus kochii, Archosauromorpha Terrestrisuchs, Crocodylomorpha

  24. Today’s reading Ediacara fauna and the origin of Metazoa: http://www.peripatus.gen.nz/paleontology/Ediacara.html http://www.ucmp.berkeley.edu/vendian/critters.html The Burgess shale: http://www.gpc.edu/~pgore/geology/geo102/burgess/burgess.htm http://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htm The history of life: http://www.palaeos.com/ The tree of life: http://www.tolweb.org/tree/ The virtual fossil museum: http://www.fossilmuseum.net/ On the cambrian explosion: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1578734 Metazoan phylogeny: the state of art.: http://icb.oxfordjournals.org/cgi/content/full/46/2/93 Dunn C. W. et al. (2008) Broad phylogenomic sampling improves resolution ofthe animal tree of life. Nature 452: 745-750. Srivastava M. et a. 2008. The Trichoplax genome and the nature of placozoans. Nature 453: 855-960..

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