HSBMB-Crocus - H ellenic Society of Biochemistry Molecular...

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From model plants to crops: the MADS – box family of gene controlling flower development in Crocus ( Crocus sativus L . ) A. Tsaftaris 1, 2 , K. Pasentsis 1 , A. Kalivas 2 , A. Polidoros 1 1 Institute of Agobiotechnology (IN.A.) - Center for Research and Technology Hellas (CERTH), Thermi,Thessaloniki, GREECE. 2 Department of Genetics and Plant Breeding, AUTH, Thessaloniki Email address: [email protected] Abstract We have cloned and characterized the structures and expression, of the familiy of flower specific MADS-Box genes of cultivated Crocus ( Crocus sativus L). The deduced amino acid sequence of the gene indicated high homology with members of the MADS-box family of transcription factors. In contrast to PISTILLATA (PI) and APETALLA3 (AP3) studies of other plants monocots and dicots and the predictions of the ABC-model for floral organ identity genes, expression studies indicated the presence of the transcripts are not restricted only in the second and third whorl of the flowers but also in the petaloid sepals and stigmata of the mature crocus flower parts, explaining the homeotic transformation of sepals to petals in this species. Introduction Arabidopsis plants produce a number of closely spaced rosette leaves during the vegetative phase. Upon the transition to flowering, the internode length increases, and this event causes a significant increase in the distance that separates the last few vegetative (cauline) leaves. The flowers are composed of four whorls of organs, with sepals in the first, or outermost, whorl, petals in the second whorl, stamens in the third whorl, and carpels occupying the fourth whorl, in the center. The simple and elegant ABC model of flower development was proposed to explain the activity of the floral organ identity genes (Coen and Meyerowitz, 2001). According to the model, the combined actions of three different functions, each one active in two adjacent whorls, are responsible for the development of the four types of organs of a typical eudicot flower. The model suggests that A alone specifies sepals, C alone specifies carpels, and the combined activities of AB and BC specify petals and stamens, respectively. In Arabidopsis , APETALA1 ( AP1 ) and APETALA2 ( AP2 ) are the A function genes, APETALA3 and PISTILLATA are the B function genes, and AGAMOUS ( AG ) is the only C function gene. With the exception of AP2 , all of these genes are members of the MADS-box family of transcription factors, whose expression patterns correspond to their domains of action Today, MADS box research is revealing a much more detailed and complex picture from the initial ABC model. Whereas the original ABC model was based largely on the analysis of flower developmental mutants using classic forward-genetics approaches, recent progress using reverse-genetics strategies has revealed redundant functions that were missed before. Likewise, recent studies using protein-protein interactions to elucidate complex interaction scheme than the originally proposed heterodimer formation between the B-
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HSBMB-Crocus - H ellenic Society of Biochemistry Molecular...

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