U.S. Department of Energy, Office of Science

Poplar Genome Based Research for Carbon Sequestration in Terrestrial Ecosystems
Principal investigator:
Jonathan R. Cumming, West Virginia University
jcumming@wvu.edu

Co-investigators:
Aaron Timperman and Dale Karlson, West Virginia University

Project period:
November 2005 to present


ER64148 		  Exudation by poplar ectomycorrhizas: qualitative and quantitative assessment of carbon sequestration

Summary: Sequestration of carbon by forests comprises a suite of processes, including photosynthesis, growth, and the accumulation of organic matter in soils. Of the fluxes and pools in the forest carbon sequestration system, data for the rates and types of carbon partitioning to root and symbiotic mycorrhizal exudation represent a weak and variable part of present understanding of the carbon cycle.

Patterns of carbon flux into the rhizosphere of hybrid poplar clones associating with the ectomycorrhizal fungi Laccaria bicolor and Pisolithus tinctorius are being assessed. The approach includes integration of whole-plant physiology and growth, analytical chemistry, and molecular biology to:

  • assess influences of ectomycorrhizal fungi on the fluxes of carbon to the rhizosphere,
  • characterize chemical forms of exudates,
  • investigate changes in gene expression resulting from mycorrhizal colonization and identify plant and fungal genes associated with exudation, and
  • assess effects of ectomycorrhization on variation of carbon fluxes in poplar genotypes.

Specific hypotheses are that:

  • ectomycorrhizal fungi (ECM) increase expression of genes of carbon processing metabolic pathways in host roots,
  • production of extramatrical hyphae is a large component of carbon sequestration in the rhizosphere,
  • ECM increase the release of carbon into the rhizosphere through changes in (a) organic acids, (b) carbohydrates and (c) previously unidentified carbon-containing compounds not produced by non-mycorrhizal poplar roots, and
  • ECM colonization reduces the variation in both gene expression associated with carbon processing present among poplar clones and exudation of carbon into the rhizosphere by poplar clones.
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