FRUITFULL

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The FRUITFULL gene (previously called AGL8) is closely related in sequence to the flower meristem identity genes APETALA1 (AP1) and  CAULIFLOWER, although its expression pattern is quite distinct from these two genes. FUL RNA is dramatically up-regulated  upon the transition from vegetative to reproductive development, where its expression is detected in cauline leaves, stems, and in  flowers and fruits.  During flower and fruit development, FUL RNA is detected at high levels in the valves.

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Gene Sequence

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FUL RNA (red) is detected at high levels in the inflorescence meristem beginning at around the transition to reproductive growth (left). Interestingly, FUL RNA is absent from stage 1 and stage 2 flower primordia as they arise on the flanks of the inflorescence meristem. At  around stage 3 of flower development, FUL RNA begins to accumulate in the central region that will later give rise to carpels. Later in flower and fruit  development, FUL RNA is restricted to the valves of the developing carpels, as seen by the cross-section (right).

The most dramatic phenotype caused by mutations in FUL is a failure of the fruit to elongate post fertilization.  Consistent with its expression pattern, ful-mutant valve cells fail to grow and differentiate, indicating that FUL is required to specify a valve cell identity.

 

Example of the premature bursting of a ful silique due to failure of the fruit to elongate.

 
In addition, mutations in ful dramatically enhance the phenotype of ap1 cal double mutants.  The “cauliflower” phenotype characteristic of ap1 cal double mutants is caused by a proliferation of inflorescence-like meristems.  However, later in plant development, ap1 cal double mutants produce flowers and fruits.  In contrast, the ful ap1 cal triple mutant never flowers and instead produces ‘leafy shoots’.

ap1 cal double muants (left) and ap1 cal ful triple mutant (right)
Selected References:

Mandel, A.M. and Yanofsky, M.F. (1995) The Arabidopsis AGL8 MADS-box gene is expressed in inflorescence meristems and is negatively regulated by APETALA1. Plant Cell 7:1763-1771.

Ferrandiz C, Gu Q, Martienssen R, Yanofsky M.F. (2000) Redundant regulation of meristem identity and plant architecture by FRUITFULL, APETALA1 and CAULIFLOWER. Development 127, 725-734

Gu Q, Ferrandiz C, Yanofsky M.F., Martienssen R (1998) The FRUITFULL MADS-box gene mediates cell differentiation during Arabidopsis fruit development. Development 125, 1509-1517 (1998)

Purugganan, M.D., Rounsley, S.D., Schmidt, R.J., and Yanofsky, M.F. (1995). Molecular evolution of flower development: diversification of the plant MADS-box regulatory gene family. Genetics 140:345-356.