RESUMO
Localized wounding of one leaf in intact tomato (Lycopersicon esculentum Mill.) plants triggers rapid systemic transcriptional responses that might be involved in defense. To better understand the mechanism(s) of intercellular signal transmission in wounded tomatoes, and to identify the array of genes systemically up-regulated by wounding, a subtractive cDNA library for wounded tomato leaves was constructed. A novel cDNA clone (designated LebZIP1) encoding a DNA-binding protein was isolated and identified. This clone appears to be encoded by a single gene, and belongs to the family of basic leucine zipper domain (bZIP) transcription factors shown to be up-regulated by cold and dark treatments. Analysis of the mRNA levels suggests that the transcript for LebZIP1 is both organ-specific and up-regulated by wounding. In wounded wild-type tomatoes, the LebZIP1 mRNA levels in distant tissue were maximally up-regulated within only 5 min following localized wounding. Exogenous abscisic acid (ABA) prevented the rapid wound-induced increase in LebZIP1 mRNA levels, while the basal levels of LebZIP1 transcripts were higher in the ABA mutants notabilis (not), sitiens (sit), and flacca (flc), and wound-induced increases were greater in the ABA-deficient mutants. Together, these results suggest that ABA acts to curtail the wound-induced synthesis of LebZIP1 mRNA.
Assuntos
Proteínas de Ligação a DNA/genética , Zíper de Leucina/genética , Proteínas de Plantas/genética , Solanum lycopersicum/genética , Fatores de Transcrição/genética , Dedos de Zinco/genética , Ácido Abscísico/fisiologia , Sequência de Aminoácidos , Sequência de Bases , Fatores de Transcrição de Zíper de Leucina Básica , Clonagem Molecular , DNA Complementar , DNA de Plantas , Fatores de Ligação G-Box , Dosagem de Genes , Regulação da Expressão Gênica de Plantas , Dados de Sequência Molecular , RNA Mensageiro/metabolismo , Homologia de Sequência de AminoácidosRESUMO
It has been shown that tomato (Lycopersicon esculentum) plants respond to flame wounding and electrical stimulation by a rapid (15 min) and systemic up-regulation of proteinase inhibitor (pin) genes. To find other genes having a similar expression pattern, we used subtractive cDNA screening between flamed and control plants to select clones up-regulated by flame wounding. We report the characterization of one of them, a chloroplast mRNA-binding protein encoded by a single gene and expressed preferentially in the leaves. Systemic gene expression in response to flaming in the youngest terminal leaf exhibited three distinct phases: a rapid and transient increase (5-15 min) in transcript accumulation, a decline to basal levels (15-45 min), and then a second, more prolonged increase (60-90 min). In contrast, after a mechanical wound the rapid, transient increase (5 min) was followed by a rapid decline to basal levels but no later, prolonged accumulation. In the petiole, the initial flame-wound-evoked transient increase (15 min) was followed by a continuous decline for 3 h. The nature of the wound signal(s) causing such rapid changes in transcript abundance is discussed in relation to electrical signaling, which has recently been implicated in plant responses to wounding.
Assuntos
Cloroplastos/metabolismo , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/genética , Solanum lycopersicum/fisiologia , Transcrição Gênica , Sequência de Aminoácidos , Estimulação Elétrica , Temperatura Alta , Cinética , Solanum lycopersicum/genética , Dados de Sequência Molecular , Folhas de Planta , Proteínas de Ligação a RNA/química , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Spinacia oleracea/genética , Spinacia oleracea/metabolismo , Tetraspanina 28 , Fatores de TempoRESUMO
In Bidens pilosa (cv. radiata), a non-injurious stimulus induces a local and transient change in membrane potential, and an injurious stimulus induces a transmitted electrical signal described as the combination of an action potential and a slow wave. We have studied calmodulin gene expression after these stimuli. When the stimulus is non-injurious, calmodulin mRNA accumulation is only increased in the stimulated region. In contrast, when the stimulus is injurious, mRNA accumulation takes place in both wounded and distant, unwounded tissue. We propose that the slow wave plays a role in the long-distance transmission of a wound-induced information in plants.
