evolution of flower development - university of...
TRANSCRIPT
Zahn et al. (2005)
Developmental processes that occur in the flowers
different taxa.
Infer evolutionary events that led to the differences
or similarities.
Using the Evo-Devo Approach to study floral diversity
Floral diversity is generated by different mature morphologies
Phyllotaxy
Whorl Number
Organ Fusion
Organ Identity
Organ Elaboration
Symmetry
Reverse Genetics - Floral Symmetry controlled by CYCLOIDEA(CYC) and
DICHOTOMA(DICH) Antirrhinum majus
Luo et al. (1996)
CYC expression in developing flowers
WT Peloric
Linaria vulgaris
Linaria vulgaris peloric mutant
Bilateral Symmetry has evolved many times
Carl Linneaus 1707-1778
Forward genetics - L. vulgaris peloric mutations caused by methylation of CYCLOIDEA
Hileman et al. (2003)
Mohavea confertiflora - Changes in symmetry with an evolutionary effect
Cubas (2004)
Floral Organ Identity genes are MADS Box genes = Transcription Factors
HOX Genes
HOX genes in animals are important for
correct body-plan formation.
MADS-Box genes in flowers are
important for correct organ identity.
“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
Arabidopsis thaliana Antirrhinum majus
Homeotic Mutants – used to study HOX genes in Drosophila
Carroll et al. (2005).
HOX Genes
WT
antennapedia
Homeotic conversions of floral organs to study gene function in flower development
C-class gene in Arabidopsis = AGAMOUS
B
A C STA C A R
B B
SEP PE T
“Sliding Boundary” model is one modification to the ‘ABC’ Model
Kramer et al. (2003)
PE T PE T SEP SEP
T. thalictroides Horticultural Mutants
Wildtype ‘Betty Blake’ ‘Shoaf’s Double’
‘Green Dragon’ ‘Double White’
Theophrastus 371-287 BC
Double Flowers – the first recorded floral mutants
Arabidopsis WT
Arabidopsis agamous mutant
T. thalictroides WT
T. thalictroides ‘Double White’
Thalictrum C-class genes
2 AGAMOUS (AG) orthologs: ThAG1 and ThAG2
Kramer et al. 2004
ThdAG2 carpellate flower
ThdAG1 carpellate flower
ThdAG1 staminate flower
Di Stilio et al. 2005
Forward Genetics – ‘Double White’ has a defect in ThAG1
T. thalictroides WT
T. thalictroides ‘Double White’
T. thalictroides WT
T. thalictroides TRV2ThAG1
Viral Induced Gene Silencing (VIGS)
Reverse Genetics – Down-regulating ThAG1 creates a ‘double flower’ phenotype
T. thalictroides ‘Double White’