CHAN Raquel Lia
capítulos de libros
Homeodomain-leucine zipper proteins participating in abiotic stress response in plants
Plant Stress and Biotechnology
Lugar: Jaipur-India; Año: 2007; p. 1 - 11
Development in multicellular organisms results from growth and differentiation and is determined by a specific program of gene expression. In plants, environmental factors have a great influence on development via different signal transduction pathways that amplify the original signal and ultimately result in the activation or repression of certain genes. The synthesis of most eukaryotic proteins is regulated at the transcriptional level. Such a coordinated regulation depends on the activity of a group of proteins generally called transcription factors, which are able to enhance or reduce the rate of transcription by facilitating the assembly of the initiation complex. A typical minimum promoter extends about 100 bp upstream of the transcription initiation site and includes several sequence elements named proximal promoter sequences. The promoter sequences that interact with transcription factors are termed cis-acting elements while transcription factors that bind these cis-acting sequences are called trans-acting factors. Cis-acting elements that are far before the proximal promoter can exert either positive or negative control and are termed distal regulatory sequences. Distal cis-acting elements involved in gene regulation by hormones and other signaling agents are called response elements. Coming to trans-acting elements, it is possible to identify in a typical transcription factor, three structural features: a DNA binding domain, a transcription-activating domain and a ligand-binding domain. The DNA-binding domain must be able to set extensive interactions with the DNA by forming hydrogen, ionic and hydrophobic bonds. Analysis of many plant DNA-binding proteins has led to the identification of a number of highly conserved structural motifs, such as helix turn helix, zinc-finger, helix-loop-helix, leucine and basic-zipper. Homeodomain proteins are a particular class of helix-turn-helix proteins [1]. The interaction between cis- and trans- acting factors plays a key role in determining the development program in plants as well as in other eukaryotic organisms. This program consists of a precise spatial and temporal pattern of gene expression, influenced by external agents in the plant kingdom. More recently, silencing led by non coding micro-RNAs has been described as an additional mechanism of post-transcriptional regulation [2].