Genetic control of floral size and proportions

Abstract

Floral size is an ecologically important trait related to pollination success and genetic fitness. Independently of the sexual reproduction strategy, in many plants, floral size seems to be controlled by several genetic programs that are to some extent independent of vegetative growth. Flower size seems to be governed by at least two independent mechanisms, one controlling floral architecture that affects organ number and a second one controlling floral organ size. Different organ-dependent growth control may account for the final proportions of a flower as a whole. Genes controlling floral organ identity, floral symmetry and organ polarity as well as auxin and gibberellin response, also play a role in establishing the final size and architecture of the flower. The final size of an organ seems to be controlled by a systemic signal that might in some cases overcome transgenic modifications of cell division and expansion. Nevertheless, modification of basic processes like cell wall deposition might produce important changes in the floral organs. The coordination of the direction of cell division and expansion by unknown mechanisms poses a challenge for future research. KEY WORDS: floral meristem, cell cycle, systemic signal, floral patterning, floral architectureThe final shape and body size of multicellular organisms is the result of a genetic program and the influence of environmental conditions. In animals and plants the intrinsic growth rate is modulated by nutrient availability that determines the final size of the organism. In animals, both body size and longevity are to some extent controlled by the insulin pathway that is in itself dependent on nutrient conditions (Nijhout, 2003). But one important difference between plants and animals is that in plants, the formation of the different organs happens after embryonic development, thus not only organ or body size is influenced by environmental clues but also the types of organs produced. Our understanding of the way final plant size is achieved has been obtained using two different approaches: physiologists have tried to understand the roles of the so called plant growth regulators and environmental signals on plant development whereas geneticists have concentrated their efforts in finding mutants, genes or natural variation affecting growth in any of its forms. Although these two research lines appear separate, the reality is that they have been linked by an enormous amount of work done by plant breeders studying gene and environment interactions on agricultural traits that are related to growth, like yield, fruit size, biomass production etc. The efforts done in the model system Arabidopsis have helped to bring together the more basic approaches since mutations affected in plant growth regulator synthesis, degradation and Int. J. Dev. Biol. 49: 513-525 (2005) Which are the mechanisms that control the final size of an organism is a question without a clear answer yet. There are two basic processes that could contribute to its control: cell divis...

Regulatory change at Physalis Organ Size 1 correlates to natural variation in tomatillo reproductive organ size

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Large Flower Size: Molecular Basis and Role of Cytokinin

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Corolla of the Large-flowered Petunia (Petunia hybrida Vilm.) Cultivars Exhibit Low Endogenous Cytokinin Concentration through Enhanced Expression of the Genes Encoding Cytokinin Oxidases

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