09-Biologia Plantarum - crocus AG1

09-Biologia Plantarum - crocus AG1 - BIOLOGIA PLANTARUM 49...

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BIOLOGIA PLANTARUM 49 (4): 499-504, 2005 499 Isolation of a differentially spliced C-type flower specific AG -like MADS-box gene from Crocus sativus and characterization of its expression A.S. TSAFTARIS* , ** ,1 , K. PASENTSIS* and A.N. POLIDOROS* Institute of Agrobiotechnology, CERTH, Thermi, GR-57001, Greece* Department of Genetics and Plant Breeding, AUTH, Thessaloniki, GR-54006, Greece** Abstract We have cloned and characterized the expression of Crocus sativus AGAMOUS1 ( CsAG1 ), a putative C-type MADS- box gene homologous to AGAMOUS ( AG ) from a triploid monocot species crocus ( Crocus sativus L.). The typical domain structure of MIKC-type plant MADS proteins was identified. Phylogenetic analysis of the deduced amino acid sequence indicated that the isolated gene forms a clade with the AGAMOUS homologs from the monocots Hyacinthus orientalis and Phalaenopsis equestris . A differential splicing event altering the amino acid sequence at the C terminus was identified, leading to the formation of two mRNAs differing ten nucleotides in size. The presence of both differentially spliced transcripts was restricted only to mature crocus flowers and particularly to stamens and carpels. Additional key words : AGAMOUS , monocot, saffron, phylogeny. Introduction MADS-box genes encode transcription factors present in several eukaryotic organisms and contain a highly conserved sequence encoding the MADS-domain that is responsible for nuclear localization, DNA binding, dimerization and accessory factor binding (Theissen et al. 2000, Immink et al. 2002). The first isolated plant MADS-box genes were DEFICIENS ( DEF ) from Antirrhinum and AGAMOUS ( AG ) from Arabidopsis. Although initially found in floral tissues where they regulate floral organ identity, it was later established that MADS-box genes also act as regulators of various other aspects of plant development (Rounsley et al. 1995, Kim et al. 2002). It has been proposed that there are at least two lineages (type I and type II) of MADS-box genes in plants, animals and fungi (Alvarez-Buylla et al. 2000). Most of the plant MADS-box genes belong to type II and encode proteins with a stereotypic organization of four domains: the conserved ~55 amino acid (aa) MADS- domain (M), followed by the intervening (I) domain (~30 aa), the keratin-like coiled-coil (K) domain (~70 aa) and the variable C-terminal (C) domain that provides functional specificity. Therefore genes displaying this organization are called MIKC-type and are plant-specific transcriptional regulators. Subsequent work revealed in plants the existence of a large family with at least nine classes of MADS-box genes based on function and expression patterns (Nam et al. 2003). In angiosperms, at least five classes of MADS-box genes are involved in control of flower development. Particularly, the ABC model of flower development (Weigel and Meyerowitz 1994) predicts that three classes of floral MADS-box genes, encoding the A, B and C functions, act alone or in
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09-Biologia Plantarum - crocus AG1 - BIOLOGIA PLANTARUM 49...

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