RESUMO
Genetic studies demonstrate that two Arabidopsis genes, CAULIFLOWER and APETALA1, encode partially redundant activities involved in the formation of floral meristems, the first step in the development of flowers. Isolation of the CAULIFLOWER gene from Arabidopsis reveals that it is closely related in sequence to APETALA1. Like APETALA1, CAULIFLOWER is expressed in young flower primordia and encodes a MADS-domain, indicating that it may function as a transcription factor. Analysis of the cultivated garden variety of cauliflower (Brassica oleracea var. botrytis) reveals that its CAULIFLOWER gene homolog is not functional, suggesting a molecular basis for one of the oldest recognized flower abnormalities.
Assuntos
Proteínas de Arabidopsis , Arabidopsis/genética , Proteínas de Ligação a DNA/genética , Genes de Plantas , Proteínas de Homeodomínio , Proteínas de Domínio MADS , Proteínas de Plantas/genética , Alelos , Sequência de Aminoácidos , Arabidopsis/química , Arabidopsis/fisiologia , Sequência de Bases , Brassica/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/fisiologia , Teste de Complementação Genética , Hibridização In Situ , Dados de Sequência Molecular , Fenótipo , Proteínas de Plantas/química , Proteínas de Plantas/fisiologia , RNA de Plantas/genética , RNA de Plantas/metabolismoRESUMO
Mutations in the AGAMOUS (AG) gene of Arabidopsis thaliana result in the conversion of reproductive organs, stamens and carpels, into perianth organs, sepals and petals. We have isolated and characterized the putative AG gene from Nicotiana tabacum, NAG1, whose deduced protein product shares 73% identical amino acid residues with the Arabidopsis AG gene product. RNA tissue in situ hybridizations show that NAG1 RNA accumulates early in tobacco flower development in the region of the floral meristem that will later give rise to stamens and carpels. Ectopic expression of NAG1 in transgenic tobacco plants results in a conversion of sepals and petals into carpels and stamens, respectively, indicating that NAG1 is sufficient to convert perianth into reproductive floral organs.
Assuntos
Genes Homeobox , Genes de Plantas , Nicotiana/crescimento & desenvolvimento , Nicotiana/genética , Plantas Tóxicas , Sequência de Aminoácidos , Arabidopsis/genética , Sequência de Bases , Clonagem Molecular , DNA Complementar/genética , Expressão Gênica , Dados de Sequência Molecular , Especificidade de Órgãos , Fenótipo , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , RNA/genética , RNA/metabolismo , Nicotiana/anatomia & histologia , Fatores de Transcrição/genéticaRESUMO
Genetic studies suggest that three homeotic functions, designated A, B, and C, act alone and together to specify the fate of floral organ primordia in distantly related dicotyledonous plant species. To test the genetic model, we have generated transgenic tobacco plants that ectopically express the AGAMOUS gene from Brassica napus, which is necessary for the C function. Flowers on the resulting plants showed homeotic transformations of sepals into carpels and petals into stamens. These phenotypes are consistent with predictions from the genetic model, show that expression of AGAMOUS is sufficient to provide ectopic C function, and demonstrate that the structure of flowers can be manipulated in a predictable manner by altering the expression of a single regulatory gene. Furthermore, the generation of the predicted transformations by ectopic expression of the Brassica gene in transgenic tobacco indicates that gene functions are interchangeable between phylogenetically distant species.
