Flowering Time Flower Meristem Identity APETALA1 LEAFY CAULIFLOWER Flower Organ Identity A B C Fruit Development FRUITFULL SHATTERPROOF INDEHISCENT 10 13 5 2 7 12 4 9 8 3 1 6 11 The shoot apical meristem SAM Traas and Vernoux 2002 LFY AP1 and CAL are expressed in flower meristems ap1 mutants have abnormal flowers with no sepals or petals Flower meristems behave as inflorescence meristems in the ap1 cal double mutant lfy mutants have abnormal flowers with no petals or stamens All flowers are converted into leafy shoots in lfy ap1 mutants The loss of flower formation in ap1 cal mutants and in ap1 lfy mutants demonstrates that LFY AP1 and CAL are required for flower development AP1 is expressed in flower meristems sepals and petals LFY is normally expressed in flower meristems What would happen if LFY was constitutively expressed throughout the plant Constitutive expression of LFY or AP1 and CAL converts shoots into flowers and promotes early flower development flowers 35S LFY Wild type D Weigel 15 Year old aspen trees D Weigel 35S LFY transgenic aspen trees Flower in less than six months D Weigel Arabidopsis flower sepal petal stamen carpel stamen petal sepal carpel 1 2 3 4 1 2 3 A A 4 1 2 3 4 B B 1 2 3 4 C C C 4 3 2 sepal C petal A stamen 3 carpel 1 2 stamen petal sepal B B A 1 A sepals A B petals B C stamens C carpels Bowman and Meyerowitz 1991 gene protein protein structure by Schumacher et al Nature vol410 26 April 2001 petal stamen sepal carpel sepal leaf The C gene is active in cells that will form stamens and carpels A The A gene is active in cells that will form sepals and petals B The B gene is active in cells that will form petals and stamens C The C gene is active in cells that will form stamens and carpels The activities of the A and C genes do not overlap In C mutant A activity expands throughout the flower In C mutant A activity expands throughout the flower One of the functions of the C gene is to prevent A gene expression in cells that would normally form stamens and carpels In A mutant C activity expands throughout the flower In A mutant C activity expands throughout the flower One of the functions of the A gene is to prevent C gene expression in cells that would normally form sepals and petals normal flower A C stamen petal sepal sepal petal stamen carpel normal B C A mutant B B A C B C C C A C stamen petal sepal sepal petal stamen carpel normal B C A mutant B B A C B C C C A C stamen petal sepal sepal petal stamen carpel normal B C A mutant B B A C B C C C C C A C C B C stamen carpel stamen B carpel B carpel stamen stamen A stamen petal sepal sepal petal stamen carpel normal A mutant B C A mutant Sepals are converted into carpels A mutant sepals are replaced by carpels A C stamen petal sepal sepal petal stamen carpel normal B C B mutant B A A C C A A C stamen petal sepal sepal petal stamen carpel normal B C B mutant B A A C C A A C stamen petal sepal sepal petal stamen carpel normal B C B mutant B A A C C A C A A C carpel sepal sepal C carpel B sepal sepal carpel A stamen petal sepal sepal petal stamen carpel normal B mutant B C A B mutant petals are replaced by sepals A C stamen petal sepal sepal petal stamen carpel normal B C C mutant B A B A B A A A A C stamen petal sepal sepal petal stamen carpel normal B C C mutant B A B A B A A A A C stamen petal sepal sepal petal stamen carpel normal B C C mutant B A B A B A A A C C A A petal petal sepal B sepal petal petal A stamen petal sepal sepal petal stamen carpel normal C mutant B A B B A A C mutant stamens are replaced by petals C mutant carpels are replaced by a new flower C C A A petal petal sepal B sepal petal petal A stamen petal sepal sepal petal stamen carpel normal C mutant B A B B A A petal stamen sepal carpel sepal leaf The C gene is active in cells that will form stamens and carpels C AGAMOUS gene Summary The C gene is expressed in cells that will later form stamens and carpels C AGAMOUS gene Summary The C gene is expressed in cells that will later form stamens and carpels The C gene is necessary for stamen and carpel development C AGAMOUS gene Summary The C gene is expressed in cells that will later form stamens and carpels The C gene is necessary for stamen and carpel development The C gene is necessary to prevent the indeterminate growth of the flower meristem What happens if the B and C genes are both inactivated in the BC double mutant B B A stamen petal sepal C carpel C sepal petal stamen A A C stamen petal sepal sepal petal stamen carpel normal B C BC mutant B A A A A A C C A A sepal sepal sepal B sepal sepal sepal A stamen petal sepal sepal petal stamen carpel normal BC mutant B A A A BC double mutant all organs are sepals C 4 3 2 sepal C petal A stamen 3 carpel 1 2 stamen petal sepal B B A 1 What happens if the A B and C genes are all inactivated in the ABC triple mutant B B A stamen petal sepal C carpel C sepal petal stamen A A C stamen petal sepal sepal petal stamen carpel normal B C ABC mutant B A C C leaf leaf leaf B leaf leaf leaf A stamen petal sepal sepal petal stamen carpel normal ABC mutant B A ABC triple mutant all organs are leaves Goethe believed that floral organs are derived from leaves Goethe 1790 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 C stamen petal sepal A carpel sepal petal stamen normal B B C A Regulatory region stamens and carpels Remove regulatory region Add sepal regulatory region sepals C GENE Coding Region C B stamen petal petal A stamen stamen petal petal mis expression of B activity C A B mis expression of B activity stamen stamen stamen stamen stamen stamen stamen mis expression of B and C activity B B C C mis expression of B and C activity mis expression of A and B activity in C mutant B petal petal petal B A petal petal petal …
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