RESUMO
Deficiens, a homeotic gene involved in the genetic control of flower development, codes for a putative transcription factor. Upon mutation of the gene, petals are transformed to sepals and stamens to carpels, indicating that deficiens is essential for the activation of genes required for petal and stamen formation. In a search for putative target genes of deficiens, several stamen- and petal-specific genes were cloned that are expressed in wild type but not in the deficiensglobifera mutant. In this report the molecular characterization of two of these genes, tap1 and fil1, is presented. They are transiently expressed during flower development. In situ hybridization data demonstrate that tap1 is expressed in the tapetum of the anthers and fil1 in the filament of the stamen and at the bases of the petals. Both genes encode small proteins with N-terminal hydrophobic domains suggesting that they are secreted. We discuss possible functions of the gene products and their relationship to the deficiens gene.
Assuntos
Regulação da Expressão Gênica/genética , Proteínas de Plantas/genética , Plantas/genética , Sequência de Aminoácidos , Sequência de Bases , Northern Blotting , Clonagem Molecular , Sequência Consenso , Genes Homeobox/genética , Dados de Sequência Molecular , Mutação/genética , Desenvolvimento Vegetal , Sinais Direcionadores de Proteínas/genética , Endonucleases Específicas para DNA e RNA de Cadeia Simples/metabolismo , Fatores de Transcrição/genéticaRESUMO
We present the genomic structure of Tam1, a transposable element from Antirrhinum majus. The Tam1 element is 15.2 kb long and includes two genes that are transcribed to produce a 2.4 kb (tnp1) and a 5 kb mRNA (tnp2). These transcripts partially overlap and the exons are scattered over the whole element. Tnp1 encodes a 53 kDa protein as deduced from the cDNA sequence. The 5 kb transcript of tnp2 contains an open reading frame that shares 45% homology with part of the tnpD gene of En/Spm from maize and 48% homology with an open reading frame of the Tgm element from Glycine max. We discuss the possible functions of these genes by analogy with En/Spm. Additionally, a number of flanking sequences of Tam1 insertions were analysed to investigate the sequence specificity of insertion. From these studies we conclude that Tam1 transposes predominantly into AT-rich regions that can be unique as well as repetitive. No specific target sequence of insertion could be found.
Assuntos
Elementos de DNA Transponíveis/genética , Plantas/genética , Zea mays/genética , Sequência de Aminoácidos , Sequência de Bases , Northern Blotting , Southern Blotting , Mapeamento Cromossômico , Clonagem Molecular , DNA/isolamento & purificação , Dados de Sequência Molecular , Poli A/isolamento & purificação , Reação em Cadeia da Polimerase , RNA/isolamento & purificação , RNA Mensageiro , Homologia de Sequência do Ácido NucleicoRESUMO
Deficiens is a floral homeotic gene of Antirrhinum majus, mutation of which results in transformation of petals to sepals and stamens to carpels. In a search for putative target genes, controlled by this regulatory locus, cDNA clones representing genes, that are expressed in wild type but not in the deficiens mutant flowers, were isolated by differential screening. The molecular structure and the expression pattern of one of these genes, tap2, is described. Tap2 is transiently and tissue-specifically expressed in the tapetum of the anthers. It encodes a 131 amino-acids-long protein with a hydrophobic N-terminus, displaying all characteristic features of a signal peptide. This indicates that the TAP2 protein may be secreted.
