Evolution and Development of Flower Diversity. Kelsey Galimba Di Stilio Lab Department of Biology University of Washington

Transcription

1 Evolution and Development of Flower Diversity Kelsey Galimba Di Stilio Lab Department of Biology University of Washington

2 Lecture Outline Evolution of Angiosperms! The first flower! Morphological Diversity Development! Evo-Devo! ABC Model Di Stilio Lab Research! Thalictrum as a model system! C Function

3 Evolution of Angiosperms

4 What is an Angiosperm?! Wood with vessels Derived Characteristics! Double fertilization - endosperm! Pollen with columnar structures! Angiosperm = enclosed seed ovules enfolded within and protected within two layers.! Flowers! both reproductive organs on the same shoot.

5 Seeking the First Flower Magnoliaceae - current Archaefructas mya? Fossil grass flower 94 mya 2.2 mm.

6 Seeking the First Flower

7 Amborella trichopoda The most similar living flower to the world s first flower Jim Doyle, UC Davis - Dioecious -!2 whorls of undifferentiated sepals/petals -!Organs arranged in a spiral -!Indeterminate numbers or organs

8 Darwin s Abominable Mystery! How can angiosperms be so diverse?!

9 When did Angiosperms Originate?

10 Floral diversity is generated by varying many aspects of floral development, including: Symmetry Phyllotaxy Merosity Organ Fusion Organ Identity Whorl Number Organ Elaboration

11 Evo-Devo: The Components Evolution Three principles: Variation Heredity Natural Selection Development The process of growing to maturity. Floral Development The initiation of the floral meristem to the mature flower.

12 Evo-Devo: The Logic! Morphology is the product of development.! Development is the product of genetic regulatory programs.! Evolution of diversity (morphology) is directly related to the evolution of genetic regulatory programs.! A limited number of genetic pathways have been used and re-used to build different body plans.

13 Evo-Devo: The Questions! How are different taxa related phylogenetically? What kind of developmental traits did the ancestor have? How did developmental processes evolve?

14 Flower Development

15 Model Plants Arabidopsis thaliana! Antirrhinum majus!

16 ABC Model of Flower Development 'A' genes control the sepals 'A' and 'B' genes in combination control the petals 'B' and 'C' genes in combination control the stamens 'C' genes control the carpels

17 ABC genes are MADS Box genes = Transcription Factors Transcription Factors control expression levels of genes. HOX Genes MADS-Box genes in flowers are important for correct organ identity. HOX genes in animals are important for correct body-plan formation.

18 Homeotic Mutants From Carroll S.et al, From DNA to diversity

19 Homeotic conversions of floral organs to study gene function.

20 Sliding Boundary model and predicted floral phenotypes! B B B A C SEP PET PET SEP STA CAR Kramer, E. M., V. S. Di Stilio and P. Schluter Complex patterns of gene duplication in the APETALA3 and PISTILLATA lineages of the Ranunculaceae. Int. J. Pl. Sci. 164 (1): 1-11.!

21 Extended ABC Model A, B, C, D, and E genes Arabidopsis E mutant -ABC mutant? Alles et Blatt -!Johann Wolfgang von Goethe

22 Land Plant ABCs A lineage Floral homeotic gene lineage established (B,C,E)

23 Back to the First Flower - Gymnosperms have reproductive organs on different shoots. Most angiosperms have flowers that are hermaphroditic on the same shoot Mostly Male Hypothesis - Possible ectopic expression of C genes on a male shoot to form the first hermaphrodite Gerhard Leubner The Seed Biology Place

24 Di Stilio Lab Research

25 Thalictrum

26 Ranunculaceae

27 Floral diversity in genus Thalictrum T. rochebrunianum T. alpinum T. kiusianum T. aquilegifolium T. dasycarpum! 190 species! Herbaceous perennials with nectarless, apetulous flowers! Variability of perianth type! Unisexual flower development without selective abortion of organs! 4 Breeding systems: hermaphroditic, dioecious, andromonoecious, gynoecious! 2 pollination mechanisms: insect and wind! Pivotal phylogenetic position

28 Geographic distribution of Thalictrum "#$%$&'()*+,!'-!.+-)/!011(233www.eol.org

29 Evolution of Pollination Syndromes Combined ITS rpl16 petal loss Pollination Insect Mixed Wind Unknown dasycarpum revolutum coriaceum pubescens cooleyi? delavayi minus flavum ramosum? aquilegifolium grandifolium? tripeltiferum? decipiens alpinum fendleri? polycarpum dioicum sparsiflorum thalictroides clavatum Paraquilegia Leptopyrum Enemion Aquilegia Dioecy Andromonoecy Dioecy Brunnet & Liston

30 Thalictrum by Pollination Type 456"78! T.rochebrunianum T. thalictroides 9:8;! T. pubescens <45=! T. fendleri! T. arsenii! T.aquilegifolium T. delavayi T. uchiyamai! T. flavum T. alpinum! T. guatemalensis T. hernandezii T. dasycarpum!

31 Thalictrum thalictroides Anemonella thalictroides Rue-Anemone!!! Geographic distribution: Eastern US Breeding System: Hermaphroditic Pollination System: Insect

32 T. thalictroides Horticultural Mutants Wildtype Betty Blake Shoaf s Double Green Dragon Double White

33 Model System: Thalictrum What we study: MADS-box Transcription Factors AKA: Organ Identity Genes AKA: ABC Genes Why? Studying the genes that control organ identity and development in a basal eudicot can shed light on how developmental processes in core eudicots evolved. Duplication events are common in MADS-box genes. This allows for sub and neo-functionalization which is theorized to create diversity.

34 Duplication in C-function gene, AGAMOUS Thalictrum has 2 AGAMOUS (AG) orthologs: ThAG1 and ThAG2 ThAG2 falls within the AG (C-class) lineage, not the AGL 11 (Dclass lineage) >,0#!)1!,&?!@AAB!

35 ABC Model In Arabidopsis, AG is expressed in stamens and carpels. In Thalictrum, AG1 is expressed in stamens and carpels, AG2 expression is limited to ovules. Ovules AG2 Expression T. diocum

36 VIGS Viral Induced Gene Silencing Burch-Smith TM, et al. 2004!Uses the plant antiviral defense system - Post Transcriptional Gene Silencing (PTGS)!Homology dependent sequence specific degradation of mrna

37 Phytoene Desaturase (PDS) as a marker for silencing Carpels in WT T. thalictroides are green

38 ThAG1 silencing in Thalictrum results in the same phenotype as the Arabidopsis ag mutant. Arabidopsis WT Arabidopsis ag mutant T. thalictroides WT T.thalictroides AG-1 VIGS

39 TthAG2_PDS VIGS

40 Molecular Validation Downregulation of ThAG2 RT AG-2 Expression Actin Expression ThAG-2 VIGS Untreated ThAG-2 VIGS Untreated

41 Do ThAG-2 silenced carpels have defective ovules? WT

42 Scanning Electron Microscopy Ovules WT TthAG2 VIGS

43 Confocal Microscopy Ovules

44 The End