INVESTIGATORS: G.A. Tuskan,1 U.C. Kalluri,1 S.D. Wullschleger,1 G.T. Howe,2 S.P. DiFazio,3 G.T. Slavov3
INSTITUTIONS: 1Environmental Sciences Division, Oak Ridge National Laboratory; 2Oregon State University, 3West Virginia University
NON-TECHNICAL SUMMARY: Maximizing biomass production on a per-unit-land-area-basis will require the development of high-yielding cultivars that maintain productivity under competition for light and other resources. The shade-avoidance syndrome, which results from competition to light, is mediated by plant photoreceptors (phytochrome) and is known to negatively impact plant productivity as resources are directed towards stem elongation and away from harvestable yield and radial increment. Comprehensive understanding and suitable modulation of shade-avoidance syndrome, therefore, has important implications in maximizing carbon capture per unit land area.
OBJECTIVES: The overall goal of the project is to determine the genetic basis and molecular controls of the shade-avoidance syndrome in hybrid poplar. Specifically, we seek to explore the 1) genes and gene networks associated with the shade-avoidance syndrome, 2) relative roles of the various phytochrome photoreceptors in the shade-avoidance syndrome, and 3) correlation between sequence variations in phytochrome genes and quantitative variation in a set of characteristic shade avoidance features (phenotype).
APPROACH: Obj. 1. We will use gene expression microarrays to examine the rapid response of phytochrome genes and identify other genes that have light (i.e., R:FR ratio)-regulated patterns of expression associated with the shade-avoidance syndrome. We will also characterize light signal transduction mechanisms as they relate to internode elongation, apical dominance, leaf area development and branching in shade-modulated plants grown in the greenhouse and growth chambers.
Obj. 2. We will modify the levels of phytochromes in cisgenic plants and measure 1) the resulting changes in plant architecture, 2) gene expression associated with the shade-avoidance syndrome, and 3) individual-tree and stand-level performance at various planting densities in the greenhouse. Expected phenotypes include plants with narrow crowns, prolific branching, and minimal self-thinning in densely-planted stands.
Obj. 3. We will 1) collect and phenotype P. trichocarpa genotypes from natural populations along a wide latitudinal transect, 2) measure population-level expression of phytochrome genes in a common-garden test, and 3) estimate the correlative relationship between phytochrome sequence variations and the observed quantitative variation in the shade avoidance phenotype variation.
Name: G.A. Tuskan