Gene expression patterns of trembling aspen trees following long‐term exposure to interacting elevated CO₂ and tropospheric O₃

Abstract

Summary• Expression of 4600 poplar expressed sequence tags (ESTs) was studied over the [2001][2002] growing seasons using trees of the moderately ozone (O 3 )-tolerant trembling aspen ( Populus tremuloides ) clone 216 exposed to elevated CO 2 and /or O 3 for their entire 5-yr life history.• Based on replication of the experiment in years 2001 and 2002, 238 genes showed qualitatively similar expression in at least one treatment and were retained for analysis. Of these 238 genes, 185 were significantly regulated (1.5-fold) from one year to the other in at least one treatment studied. Less than 1% of the genes were regulated 2-fold or more.• In the elevated CO 2 treatment, relatively small numbers of genes were upregulated, whereas in the O 3 treatment, higher expression of many signaling and defense-related genes and lower expression of several photosynthesis and energyrelated genes were observed. Senescence-associated genes (SAGs) and genes involved in the flavanoid pathway were also up-regulated under O 3 , with or without CO 2 treatment. Interestingly, the combined treatment of CO 2 plus O 3 resulted in the differential expression of genes that were not up-regulated with individual gas treatments.• This study represents the first investigation into gene expression following longterm exposure of trees to the interacting effects of elevated CO 2 and O 3 under field conditions. Patterns of gene-specific regulation described in this study correlated with previously published physiological responses of aspen clone 216.

The physiological, transcriptional and genetic responses of an ozone- sensitive and an ozone tolerant poplar and selected extremes of their F 2 progeny

“…Many of the differentially expressed genes identified here as being ozone-responsive, confirm previous studies on other species (Gupta et al, 2005;Li et al, 2006;Matsuyama et al, 2002;Puckette et al, 2008). Genes identified here are also more generally involved in abiotic stress responses.…”

Effects of abiotic stress on gene transcription in European beech: ozone affects ethylene biosynthesis in saplings of Fagus sylvatica L.

“…3). Ozone induction of ACO1 and ACO2 transcripts has also been reported recently in leaves of 3-yearold beech saplings (Olbrich et al 2005, Nunn et al 2005a) and in moderately ozonetolerant aspen clones in a free-air ozone fu- a b migation study (Gupta et al 2005). Interestingly, ACO1 and ACO2 were much more strongly induced in ozone-sensitive than in ozone-resistant birch clones, again favouring the notion that beech saplings are ozonesensitive.…”

Deciphering the ozone-induced changes in cellular processes: a prerequisite for ozone risk assessment at the tree and forest levels

“…The drastic decrease in chlorophyll and Rubisco contents is correlated with accelerated leaf senescence (Miller et al 1999). Genes involved in senescence and protein turnover are upregulated in Populus tremuloides leaves exposed to O 3 (Gupta et al 2005). Early senescence would restrict the "return on investment" in leaf buildup and therefore drastically affect plant carbon budget.…”