RESUMO
A gene encoding a globulin from a major taro (Colocasia esculenta L. Schott) corm protein family, tarin (G1, ca. 28 kDa) was isolated from a lambda Charon 35 library, using a cDNA derived from a highly abundant corm-specific mRNA, as probe. The gene, named tar1, and the corresponding cDNA were characterized and compared. No introns were found. The major transcription start site was determined by primer extension analysis. The gene has an open reading frame (ORF) of 765 bp, and the deduced amino acid sequence indicated a precursor polypeptide of 255 residues that is post-translationally processed into two subunits of about 12.5 kDa each. The deduced protein is 45% homologous to curculin, a sweet-tasting protein found in the fruit pulp of Curculigo latifolia and 40% homologous to a mannose-binding lectin from Galanthus nivalis. Significant similarity was also found at the nucleic acid sequence level with genes encoding lectins from plant species of the Amaryllidaceae and Lilliaceae families.
Assuntos
Genes de Plantas/genética , Globulinas/genética , Lectinas de Ligação a Manose , Proteínas de Plantas/genética , Caules de Planta/genética , Verduras/genética , Sequência de Aminoácidos , Sequência de Bases , Galanthus , Biblioteca Genômica , Globulinas/química , Globulinas/isolamento & purificação , Globulinas/fisiologia , Lectinas/genética , Dados de Sequência Molecular , Lectinas de Plantas , Proteínas de Plantas/química , Proteínas de Plantas/isolamento & purificação , Proteínas de Plantas/fisiologia , RNA de Plantas/genética , Seleção Genética , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Distribuição TecidualRESUMO
In search of establishing a system for genetic transformation of Brazilian potato cultivars, Agrobacterium tumefaciens carrying the plasmid pGV1040, was used to transform leaf discs of three cultivars of local importance, i.e., Aracy, Baronesa and Mantiqueira. This plasmid contains marker genes for resistance to kanamycin and phosphinothricin plus the gene for the enzyme ß-glucuronidase. A two step regeneration/selection procedure produced shoots of potato cultivar Mantiqueira with in vitro resistance to kanamycin and to phosphinothricin. After transfer to the greenhouse, the potentially transgenic plants, sprayed with the herbicide Finale(®) (20% a.i.; Hoechst(®)) remained green as compared to control clones that died immediately afterwards. Southern blot analysis and histochemical and fluorimetric assay for ß-glucuronidase indicated that the gene coding for the enzyme was integrated in the potato genome and could be expressed in potato tissues. No success was obtained for transformation of cultivars Aracy and Baronesa using this procedure.