Download Testing the ABC floral

Testing the ABC floral-organ
identity model: Double Mutants
Objectives:
To test the validity of the ABC model for floral organ identity we will:
1.
Use the model to make predictions concerning the phenotype of double
or triple loss-of-function mutants and compare with the actual double
mutant phenotypes.
2.
Clone and sequence the ABC genes. Look for similarities with
sequenced genes already in the database.
3.
Determine the time and place of expression for each ABC gene and
consider whether the expression correlates with the functional domain
defined by the loss-of-function phenotype.
4.
Test regulatory interactions between ABC genes by examining how the
loss-of-function of one gene affects the expression domain of another.
5.
Create gain-of-function mutants by generating transgenic plants carrying
an ABC gene cDNA under the control of the CaMV35S promoter.
A Model For Control of Organ Type
Mutations in Classes B and C function genes
Wild type
sepal
petal
1
2
stamen
carpel
4
3
B (AP3, PI)
A (AP2)A (AP2) C (AG)
B C Double
Mutant
Expected:
sepal
sepal
sepal
sepal
Construction of ap3, ag double
mutant
ap3/ap3, AG/AG x AP3/AP3,AG/ag
Wild type
F1 AP3/ap3, AG/ag
X AP3/ap3, AG/ag
F2
99 wild type; 37 Ag; 31 Ap3; 9 AgAp3
expected: 99
33
33
11
ap3, ag double mutant
A Model For Control of Organ Type
Mutations in Classes B and C function genes
Wild type
sepal
petal
1
2
stamen
carpel
3
4
A (AP2)
B C Double
Mutant
Expected:
sepal
sepal
sepal
sepal
Observed:
sepal
sepal
sepal
sepal
A Model For Control of Organ Type
Mutations in Classes A and B function genes
Wild type
sepal
petal
1
2
stamen
carpel
4
3
B (AP3, PI)
A (AP2)
C (AG)
A B Double
Mutant
Expected:
carpel
carpel
C (AG)
carpel
carpel
ap3, ap2 double mutant
A Model For Control of Organ Type
Mutations in Classes A and B function genes
Wild type
sepal
petal
1
2
stamen
3
carpel
4
C (AG)
A B Double
Mutant
Expected:
carpel
carpel
carpel
carpel
Observed:
carpel
carpel
carpel
carpel
A Model For Control of Organ Type
Mutations in Classes A and C function genes
Wild type
sepal
petal
1
2
stamen
carpel
4
3
B (AP3, PI)
A (AP2)
A C Double
Mutant
Expected:
?
?
C (AG)
?
?
ap2, ag double mutant
A Model For Control of Organ Type
Mutations in Classes A and C function genes
Wild type
sepal
petal
1
2
stamen
3
carpel
4
B (AP3, PI)
A C Double
Mutant
Expected:
Observed:
?
?
Leaf/sepal/ Petal\
carpel
Stamen
?
?
Petal\
Leaf/sepal/
Stamen carpel
A Model For Control of Organ Type
Mutations in Classes A, B and C function genes
Wild type
sepal
petal
1
2
stamen
carpel
4
3
B (AP3, PI)
A (AP2)
A B C Triple
Mutant
Expected:
?
?
C (AG)
?
?
ap2 ap3, ag triple mutant
A Model For Control of Organ Type
Mutations in Classes A, B and C function genes
Wild type
A B C Triple
Mutant
Expected:
Observed:
sepal
petal
stamen
1
2
3
4
?
leaf
?
leaf
?
leaf
?
leaf
carpel
Apetala1 Mutant
APETALA1 Gene
• In the typical Ap1 mutant phenotype the floral perianth
organs are replaced by one or two leaves and branches.
• However, some mutant alleles of AP1 result in a
phenotype like Ap2 (perianth replaced by stamens and
carpels.
• Thus AP1 is considered to regulate two processes: shoot
identity and Class A floral organ type.