|Ainsworth, Elizabeth - Lisa|
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2006
Publication Date: 9/1/2006
Citation: Ainsworth, E.A., Rogers, A., Vodkin, L.O., Walter, A., Schurr, U. 2006. The effects of elevated [CO2] on soybean gene expression. An analysis of growing and mature leaves. Plant Physiology. 142:135-147. Interpretive Summary: Elevated carbon dioxide concentration stimulates soybean leaf growth and canopy area development, but the genetic mechanisms for this response are unknown. We investigated the effects of higher carbon-dioxide levels anticipated for the year 2050 on soybean gene expression patterns. These experiments were done in both rapidly expanding and mature leaves. We found that elevated carbon dioxide concentration stimulated genes involved in cell growth and cell proliferation. Further, elevated carbon dioxide stimulated transcripts involved in the respiratory breakdown of carbohydrates, which provides increased carbon skeletons for leaf expansion and growth. These findings are important to breeders who are interested in finding molecular markers for soybean responses to elevated carbon dioxide concentration.
Technical Abstract: Improvements in carbon assimilation and water use efficiency lead to increases in maximum leaf area index at elevated carbon dioxide concentration ([CO2]); however, the molecular drivers for this increase are unknown. We investigated the molecular basis for changes in leaf development at elevated [CO2] using soybeans (Glycine max) grown under fully open air conditions at the Soybean Free Air CO2 Enrichment (SoyFACE) facility. The transcriptome responses of rapidly growing and fully expanded leaves to elevated [CO2] were investigated using cDNA microarrays. We identified 1146 transcripts that showed a significant change in expression in growing vs. fully expanded leaves. Transcripts for ribosomal proteins, cell cycle and cell-wall loosening, necessary for cytoplasmic growth and cell proliferation, were highly expressed in growing leaves. We further identified 139 transcripts with a significant [CO2] by development interaction. Clustering of these transcripts showed that transcripts involved in cell growth and cell proliferation were more highly expressed in growing leaves that developed at elevated [CO2] compared to growing leaves that developed at ambient [CO2]. The 327 [CO2]-responsive genes largely suggest that elevated [CO2] stimulates the respiratory breakdown of carbohydrates, which provides increased fuel for leaf expansion and growth at elevated [CO2]. While increased photosynthesis and carbohydrate production at elevated [CO2] are well documented, this research demonstrates at the transcript and metabolite level, that respiratory breakdown of starch is also increased at elevated [CO2].