Transcript Arabidopsis thaliana

• Introduction to Development
– Eukaryotic Gene Expression
– Cellular Signaling
• Simple Eukaryotic Development: Yeast
–
Model systems
• Pattern formation; chick limbs
• Organ identity; floral development
Reading
Cpt 21, pp. 406-410
Cpt 38, pp. 747-748
Cpt 35, pp. 682-683
Plant vs. Animal Development
Responds to environment:
opportunistic
Body plan formed early:
genetically determined
Meristems
Apical
Shoot or
root=primary
growth and
development
Lateral
Secondary
growth=
thickening
Meristems
Plant tissue that remains embryonic as long as the
plant lives, allowing for indeterminate growth
shoot meristem
flower meristem
leaves, stems
flowers
shoot meristem
leaves, stems
environmental trigger
flower meristem
flowers
shoot meristem
leaves, stems
environmental trigger
signaling molecule
flower meristem
flowers
Shoot meristem
Enviromental
trigger
Signaling molecules
(plant hormone)
Flower meristem
39.17
shoot meristem
=
Shoot meristem identity
genes ON
Flower meristem identity
genes OFF
shoot meristem
flower meristem
=
Shoot meristem identity
genes ON
Flower meristem identity
genes OFF
=
Shoot meristem identity
genes OFF
Flower meristem identity
genes ON
flower meristem identity genes
organ identity genes
Four types of flower
organs
Sepal
Petal
Stamen
Carpel
30.6
Model organism to study flower organ development?
Arabidopsis thaliana
Common wall cress
Four types of flower organs
Sepal
Petal
Stamen
Carpel
21.18A
How identify these organ identity genes?
How identify these organ identity genes?
Look for mutant flowers
Three families of genes affect flower organ identity
Wildtype
Gene A mutant
Gene B mutant
Gene C mutant
21.18C
Question:
How can the products of three genes produce
four organs?
Hypothesis: Genes active in specific regions of meristem
Test: Where are Genes A, B C active?
RNA from Gene A = red dye
RNA from Gene B = yellow dye
RNA from Gene C = orange dye
21.18B
Conclusion: Hyposthesis supported:
Genes active in specific regions of meristem
What types of molecules are encoded by the
organ identity genes?
What types of molecules are encoded by the
organ identity genes?
Transcription factors
Homeotic genes
• Master regulatory genes
• Transcription factors
Homeotic genes
• First identified in fruit flies
Mutations = legs in place of antennae
Homeotic genes
First identified in fruit flies
Mutations = legs in place of antennae
Plants
Mutations = sepals in place of petals
Homeotic genes
• Master regulatory genes
• Transcription factors
• Genes that control the overall body plan of
an organism by controlling the
developmental fate of groups of cells
Organ identity Genes A, B and C are:
Transcription factors
Master regulatory genes
Plant homeotic genes
Bio 103 Home