Minisymposium 9: Global change

Abs # 22001: Effects of elevated CO₂ on the gene expression of field-grown loblolly pine

Presenter:	Moura, Catarina F, c.moura@duke.edu
Authors	Moura, Catarina F (A)   Watkinson, Jonathan  (C)   Grene, Ruth  (C)   Robert, Jackson B (A) (B)
Affiliations:	(A): Department of Biology, Duke University (B): Nicholas School of the Environment (C): Department of Plant Pathology, Physiology and Weed Science, Virginia Tech

Forest ecosystems play an important role in the global carbon cycle and are directly affected by changes in atmospheric CO₂ concentration. To better characterize ecological processes associated with the rise of atmospheric CO₂ levels, it is essential to explore the underlying physiological and molecular mechanisms present in forest trees. Some of these mechanisms are likely to involve changes in the expression of a high number of genes potentially leading to acclimation of trees to elevated CO₂. We conducted an experiment comparing patterns of gene expression in loblolly pine trees growing under two different CO₂ concentrations, “Ambient” and “Elevated” (Ambient + 200ppm), at the Duke Forest FACE site. RNA was extracted from pine needles that were sampled throughout the growing season of 2002, and hybridized to microarrays containing approximately 2000 replicated cDNA clones. Genes coding for enzymes involved in carbon metabolism, such as citrate synthase and glucose-6-phosphate isomerase, were upregulated (over expressed) in elevated CO₂ conditions. There was no evidence of differential expression on genes coding for Rubisco subunits, but some chloroplast and photosystem associated genes were downregulated under elevated CO₂ at the end of the season. The gene coding for ACC synthase, an enyme involved in ethylene synthesis and plant development, was upregulated in elevated CO₂ samples during most of the growing season, suggesting increased levels of senescence in those conditions. It is also worth noting that genes in the phenylpropanoid pathway tended to be upregulated under elevated CO₂ and oxidative stress response genes showed a strong seasonal variation. This study provides insight into the response of pine trees to a major environmental change and it contributes to a desired understanding of concerted gene regulation and regulatory networks in tree species.