Kebrom and Brutnell 2007 & Clark et al. 2006
Fri Jan 15 2010
The molecular analysis of the shade avoidance syndrome in the grasses has begun.
The shade avoidance syndrome (SAS) is a morphological and physiological response initiated by a decrease in light quantity and a change in light quality. Recent work in Arabidopsis thaliana has begun to define the molecular components of the SAS in a model dicot species, but little is known of these networks in agronomically important grasses. The focus of this review is to present a current view of the SAS in the grasses based largely on the characterization of mutants in the phytochrome signal transduction pathway and on the effects of far-red light treatments on plant growth. In cereal grasses, intense selection by plant breeders has acted to attenuate some but not all shade avoidance responses within modern crop varieties. Traditionally, breeding efforts have been focused on optimizing grain yield. However, with the recent interest in lignocellulosic-based biofuels, a new breeding paradigm may emerge to optimize biomass at the expense of grain yield. Some of the opportunities and challenges for engineering plant architecture to maximize resource use efficiency and yield by targeting the SAS in grasses are discussed.
AND
A distant upstream enhancer at the maize domestication gene tb1 has pleiotropic effects on plant and inflorescent architecture.
Although quantitative trait locus (QTL) mapping has been successful in describing the genetic architecture of complex traits, the molecular basis of quantitative variation is less well understood, especially in plants such as maize that have large genome sizes. Regulatory changes at the teosinte branched1 (tb1) gene have been proposed to underlie QTLs of large effect for morphological differences that distinguish maize (Zea mays ssp. mays) from its wild ancestors, the teosintes (Z. mays ssp. parviglumis and mexicana). We used a fine mapping approach to show that intergenic sequences approximately 58-69 kb 5' to the tb1 cDNA confer pleiotropic effects on Z. mays morphology. Moreover, using an allele-specific expression assay, we found that sequences >41 kb upstream of tb1 act in cis to alter tb1 transcription. Our findings show that the large stretches of noncoding DNA that comprise the majority of many plant genomes can be a source of variation affecting gene expression and quantitative phenotypes.
The shade avoidance syndrome (SAS) is a morphological and physiological response initiated by a decrease in light quantity and a change in light quality. Recent work in Arabidopsis thaliana has begun to define the molecular components of the SAS in a model dicot species, but little is known of these networks in agronomically important grasses. The focus of this review is to present a current view of the SAS in the grasses based largely on the characterization of mutants in the phytochrome signal transduction pathway and on the effects of far-red light treatments on plant growth. In cereal grasses, intense selection by plant breeders has acted to attenuate some but not all shade avoidance responses within modern crop varieties. Traditionally, breeding efforts have been focused on optimizing grain yield. However, with the recent interest in lignocellulosic-based biofuels, a new breeding paradigm may emerge to optimize biomass at the expense of grain yield. Some of the opportunities and challenges for engineering plant architecture to maximize resource use efficiency and yield by targeting the SAS in grasses are discussed.
AND
A distant upstream enhancer at the maize domestication gene tb1 has pleiotropic effects on plant and inflorescent architecture.
Although quantitative trait locus (QTL) mapping has been successful in describing the genetic architecture of complex traits, the molecular basis of quantitative variation is less well understood, especially in plants such as maize that have large genome sizes. Regulatory changes at the teosinte branched1 (tb1) gene have been proposed to underlie QTLs of large effect for morphological differences that distinguish maize (Zea mays ssp. mays) from its wild ancestors, the teosintes (Z. mays ssp. parviglumis and mexicana). We used a fine mapping approach to show that intergenic sequences approximately 58-69 kb 5' to the tb1 cDNA confer pleiotropic effects on Z. mays morphology. Moreover, using an allele-specific expression assay, we found that sequences >41 kb upstream of tb1 act in cis to alter tb1 transcription. Our findings show that the large stretches of noncoding DNA that comprise the majority of many plant genomes can be a source of variation affecting gene expression and quantitative phenotypes.