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Genomic Science Program

2007 Awardee

A Functional Genomics Approach to Altering Crown Architecturein Populus : Maximizing Carbon Capture in Trees Grown in Dense Plantings

INVESTIGATORS: G.A. Tuskan, 1 U.C. Kalluri, 1 S.D. Wullschleger, 1 G.T. Howe, 2 S.P. DiFazio, 3 G.T. Slavov 3

INSTITUTIONS: 1 Environmental Sciences Division, Oak Ridge National Laboratory; 2 Oregon State University, 3 West Virginia University

NON-TECHNICAL SUMMARY: Maximizing biomass production on a per-unit-land-area-basiswill require the development of high-yielding cultivars that maintainproductivity under competition for light and other resources. The shade-avoidancesyndrome, which results from competition to light, is mediated by plantphotoreceptors (phytochrome) and is known to negatively impact plantproductivity as resources are directed towards stem elongation andaway from harvestable yield and radial increment. Comprehensive understandingand suitable modulation of shade-avoidance syndrome, therefore, hasimportant implications in maximizing carbon capture per unit land area.

OBJECTIVES: The overall goal of the project is to determine the geneticbasis and molecular controls of the shade-avoidance syndrome in hybridpoplar. Specifically, we seek to explore the 1) genes and gene networksassociated with the shade-avoidance syndrome, 2) relative roles ofthe various phytochrome photoreceptors in the shade-avoidance syndrome,and 3) correlation between sequence variations in phytochrome genesand quantitative variation in a set of characteristic shade avoidancefeatures (phenotype).

APPROACH: Obj. 1. We will use gene expression microarraysto examine the rapid response of phytochrome genes and identify othergenes thathave light (i.e., R:FR ratio)-regulated patterns of expression associatedwith the shade-avoidance syndrome. We will also characterize lightsignal transduction mechanisms as they relate to internode elongation,apical dominance, leaf area development and branching in shade-modulatedplants grown in the greenhouse and growth chambers.

Obj. 2. We will modify the levels of phytochromes in cisgenic plantsand measure 1) the resulting changes in plant architecture, 2) geneexpression associated with the shade-avoidance syndrome, and 3) individual-treeand 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 will1) collect and phenotype P. trichocarpa genotypes from natural populationsalong a wide latitudinal transect, 2) measure population-levelexpression of phytochrome genes in a common-garden test, and 3) estimatethe correlative relationship between phytochrome sequence variationsand the observed quantitative variation in the shade avoidance phenotypevariation.

Name: G.A. Tuskan
Phone: 865/576-8141
Fax: 865/576-9939





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