Flower Meristem Identity Flowering Time FT Flower Meristem Identity APETALA1, LEAFY, CAULIFLOWER, (TERMINAL FLOWER) Flower Organ Identity A, B, C Fruit Development FRUITFULL, SHATTERPROOF INDEHISCENT

Goethe believed that floral organs are derived from leaves

sepal petal stamen carpel B B A C C A 1 2 3 4 3 2 1

normal flower

What gene prevents the B gene from being active in the center of flowers? sepal petal stamen carpel B A C

In SUPERMAN mutants (SUP), the B activity expands into the center of the flower and converts the two carpels into two stamens. B A C C A stamen sepal petal

Superman mutant

The SUPERMAN gene normally functions to prevent B gene activity in the center of flowers B A C C A stamen sepal petal

normal BC mutant ?? B B A C C A sepal petal stamen carpel A A A A

normal BC mutant sepal petal stamen carpel sepal sepal sepal sepal *

BC double mutant all organs are sepals

What happens if the A, B and C genes are all inactivated in the ABC triple mutant? sepal petal stamen carpel B A C

normal ABC mutant ?? sepal petal petal sepal carpel stamen stamen B A

normal ABC mutant sepal petal stamen carpel leaf leaf leaf * leaf leaf

“ABC” triple mutant all organs are leaves

Goethe believed that floral organs are derived from leaves

The C gene is active in cells that will form stamens and carpels petal stamen sepal carpel sepal leaf The C gene is active in cells that will form stamens and carpels

petal stamen sepal carpel sepal leaf What would happen if the C gene was mis-expressed in cells that would normally form sepals?

add sepal on/off switch: C GENE CODING REGION ON/OFF stamens and carpels remove on/off switch: sepals add sepal on/off switch:

normal B B A C C A sepal petal petal sepal carpel stamen stamen

Ectopic B activity sepal petal petal sepal stamen stamen stamen B A C

Ectopic B activity A C B petal petal petal petal stamen stamen stamen

Ectopic B activity

Ectopic B and C activity stamen stamen stamen stamen stamen stamen stamen

Ectopic B and C activity

Ectopic A and B activity in C mutant B A petal *

Ectopic A and B activity in a C mutant