文本发育生物学evo devo

1、Evolutionary Developmental Biology (Evo-Devo) The new synthesis of biology toward the 21st Century施威扬“The Descent of Man, and Selection in Relation to Sex”The Cambrian explosion and sudden emergence of major modern animal phylaCambrian fossilsBurgess Shale Fauna (Upper Cambrian 505 My)澄江帽天山化石群（lower

2、 Cambrian, 520-25 My)Evolution is the central theory of biologyTheodosius Dobzhansky（1900-1975）Academic career: Columbia UniversityRockefeller UniversityUniversity of California, DavisAwards: National Medal of Science “Nothing in Biology Makes Sense Except in the Light of Evolution” 1973 (American B

3、iology Teacher, Vol 35, 125-129)Darwins lifeborn into privilege, and wealth but not much of a studentwas aiming for the clergy when offered opportunity to serve as H.M.S. Beagle naturalist at age 22.2 year journey turned into 5 as the obsessive (and unstable) Captain FitzRoy mapped and remapped sout

4、hern waters, bays, rivers.began to develop reputation as his collections reached Englandwrote successful journal on the voyage of the Beaglebegan secret species notebooks in late 1830s and settled in the country with wife Emmaworked twenty years on species theory, gathering evidence, agonizing over

5、possible impact; fathered ten children upon whom he doted.Species theory finally fleshed out under pressure of similar ideas emerging from Alfred Russel WallaceThe Origin of Species. quickly sold out multiple printings.The Voyage of the BeagleGeology and Zoological fauna evidencesDarwins theory of e

6、volution1) Descent with Modification All species, both living and extinct, are descended from one or a few original forms Organized beings represent a tree, irregularly branched“2) Theory of Natural SelectionOffered ideas of how species change through competitive struggle, those most fit produce off

7、spring with similar fitness.Natural selection of inheritable variations Evolutionary biology at the genetic age: the beginningsWhy Evo-devo?Developmental BiologyHow do genes affect development?A developmental genetics view of development Which genes are important for pattern formation? When and wher

8、e are these genes active? How are they regulated? Through what mechanisms do theyinfluence animal development?Evo-DevoWhat roles did changes in the NUMBER, REGULATION and FUNCTION of developmental control genes play in evolution? 1) Identify homology in animal development 2) How do new developmental

9、 features arrive? 3) How do existing development programs change?The concept of homology: common descent Shared genes indicates common history Map distribution of genes onto animal phylogeny Terms TermsHomologs - Genes sharing similar sequencesOrthologs - Genes that are separated by speciation event

10、 (same gene in two different species)Paralogs - Genes related by duplication eventsThe basic principles of Evo-devoHomologous genes often play conserved or similar roles during development in different animalsCis-regulatory changes underlie the majority of morphological variationsTrans-regulatory ch

11、anges also contribute to developmentDiversity of segmentation patternsThe genetic basis for segmentation diversity: the Homeobox genesEdward B. Lewis (1918-2004)BornMay 20, 1918Wilkes-Barre, PennsylvaniaDiedJuly 21, 2004 (aged 86)Pasadena, CaliforniaNationalityAmericanFieldsGeneticsAlma materCalifor

12、nia Institute of TechnologyNotable awards1995 Nobel Prize in MedicineHomeotic mutations change segmental identities in DrosophilaHomeotic genes control segment formation1) Mutants transform one segment into another: e.g. Antenna Leg T3 Hindwing T2 Forewing i.e. they affect segment identity2) Found i

13、n gene complexes3) Order of genes on chromosome corresponds to order of segments influenced4) These genes regulate fate of entire segments and body regionsThe Homeobox” - a common sequencein Hox genesCo-linearity of Hox gene expressionThe Ubx gene promotes haltere formation and suppresses wing devel

14、opmentThe evolution of segmentationAnnelid (环节动物）Onychophoran (栉蚕)Myriapod （多足类）Apterygota insects (无翅亚纲，primitive wingless insects)Pterygota insects（有翅亚纲）All of the Lobopodian/Anthropod Hox genes predate Cambrian explosionComparison of Hox gene expression in different animalsUbx/Abd-A expression do

15、main demarcates segmental boundariesHox cluster duplication in vertebratesConserved Hox cluster structure and expression across speciesHox genes control vertebrate axial diversityHox genes control vertebrate axial diversityDeep conservation of the toolkit in different animal phylaSome genes are asso

16、ciated with similar processes in different phyla Eyes Pax-6/eyeless Limbs Distal-less/Dlx Heart Tinman/NKX 2-5 Segmentation hairy/HER1 engrailed AP Axis Pattern Hox genesWe infer that ancestors had these genes and might have controlled primitive forms of these structuresWhile early animals are large

17、ly unknown in the fossil record, we can rebuild an image of bilaterian ancestors from inferences about these traitsEvolution of the developmental toolkit genesWhat role did the evolution of new (more) genes play in the evolution of animals?When was the toolkit assembled and expanded during evolution

18、?What can we infer about animal ancestors from genes that are shared by their descendants?Pax6 and eye developmentConserved Pax6 expression in photoreceptors and eyesDistal-less genes control limb development in bilateriansOnychophoran Annelid Sea UrchinDrosophilaUrbilateria” - the inferred lastcomm

19、on ancestor of bilateriansCambrian explosion of bilaterian diversityGene toolkits are conserved, how do morphological diversity evolve? Morphological evolution occurs at different scales macroevolutionmacroevolution: evolution aboveabove the species level, such as origin of new designs (feathers, ve

20、rtebrates from invertebrates, jaws in fish), large scale events (extinction of dinosaurs), broad trends (increase in brain size in mammals), and major transitions (origin of higher-level phyla) microevolutionmicroevolution: evolution that occurs atat or belowbelow the level of species, such as a cha

21、nge in the gene frequency of a population of organisms or the process by which new species are created (speciation)Evo-devo occurs by both cis- and trans-regulatory mechanismsCis-regulatory change underlies the majority of evo-devo changes Examples: Drosophila/butterfly wing spot diversity Stickleba

22、ck fin reduction Trans-regulatory changes also contribute to morphological evolution Example: Ubx protein sequence evolution and macroevolution of the Arthropod body planButterfly eyespot pattern diversityA new pattern of Distal-less expression marks future eyespotDistal-less stainingThe new use of

23、a toolkit gene makes the eyespots in butterfliesWing spot pattern diversity among Drosophila speciesCis-regulatory changes at the yellow locus responsible for species-specific differences in Yellow protein distributionRepeated morphological evolution throughcis-regulatory changes in the yellow enhan

24、cerCis-regulatory changes underlie rapid speciation of sticklebacks The three spine sticklebacks underwent rapid speciation in freshwater lakes during the last 10-30k yearsThe newly evolved species have distinct morphologyPitx1 and reduction of pelvic fin in freshwater sticklebacksPitx1 expressionTr

25、ans-regulatory changes in Evo-devo, a Ubx storyIn Drosophila, Ubx suppresses limb formation and is expressed in abdominal segmentsTrans-regulatory changes in Evo-devo, a Ubx storyThe C-terminus of crustacean Ubx protein lacks a QA domain as seen in HexapodEvolution of Ubx protein sequences in different animal groupsEvo-devo of human beingsLoss of an enhancer and gain of humanity Loss of an enhancer and gain of humanity Penile spines are keratinized epidermal spines overlying the penis glan