Transcriptomic comparison in the leaves of two aspen genotypes having similar carbon assimilation rates but different partitioning patterns under elevated [CO₂]
2009
Cseke, Leland J. | Tsai, Chung‐Jui | Rogers, Alistair | Nelsen, Matthew P. | White, Holly L. | Karnosky, David F. | Podila, Gopi K.
• This study compared the leaf transcription profiles, physiological characteristics and primary metabolites of two Populus tremuloides genotypes (clones 216 and 271) known to differ in their responses to long‐term elevated [CO₂] (e[CO₂]) at the Aspen free‐air CO₂ enrichment site near Rhinelander, WI, USA. • The physiological responses of these clones were similar in terms of photosynthesis, stomatal conductance and leaf area index under e[CO₂], yet very different in terms of growth enhancement (0–10% in clone 216; 40–50% in clone 271). Although few genes responded to long‐term exposure to e[CO₂], the transcriptional activity of leaf e[CO₂]‐responsive genes was distinctly different between the clones, differentially impacting multiple pathways during both early and late growing seasons. • An analysis of transcript abundance and carbon/nitrogen biochemistry suggested that the CO₂‐responsive clone (271) partitions carbon into pathways associated with active defense/response to stress, carbohydrate/starch biosynthesis and subsequent growth. The CO₂‐unresponsive clone (216) partitions carbon into pathways associated with passive defense (e.g. lignin, phenylpropanoid) and cell wall thickening. • This study indicates that there is significant variation in expression patterns between different tree genotypes in response to long‐term exposure to e[CO₂]. Consequently, future efforts to improve productivity or other advantageous traits for carbon sequestration should include an examination of genetic variability in CO₂ responsiveness.
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