Submitted to: Field Crops Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/12/2004
Publication Date: 11/1/2004
Citation: Bae, H., Sicher Jr, R.C. 2004. Changes of soluble protein expression and leaf metabolite in arabidopsis thaliana grown in elevated atmospheric carbon dioxide. Field Crops Research. 90:61-73. Interpretive Summary: Atmospheric carbon dioxide levels are increasing rapidly due to the consumption of fossil fuels. Because carbon dioxide is an important factor in plant growth, changing carbon dioxide levels are expected to impact agricultural ecosystems in the near future. The objective of this research was to determine if three times normal air levels of carbon dioxide affected gene expression of an experimental plant known as thale cress. One significant observation was that growth in elevated carbon dioxide delayed flowering in thale cress by one or two days. Total proteins, the final products of gene expression, were extracted from control and carbon dioxide enriched thale cress leaves. These proteins were separated on gels and the individual proteins were identified using information obtained from the recently published thale cress genome. Based on gel images, thirteen candidate proteins were shown to be affected either positively or negatively by carbon dioxide enrichment and six of the thirteen carbon dioxide responsive proteins were successfully identified. Functions for two of the six identified proteins were unclear due to uncertainties in the thale cress genome. Four of the identified proteins had specific functions but only one of these was involved in photosynthesis. In future, the carbon dioxide responsive proteins identified in this study will be studied in crop plants. This research will benefit other scientists and will be made available to scientists who are developing gene based crop models.
Technical Abstract: Arabidopsis thaliana L. Henyh (Columbia ecotype) plants were grown for 2 to 6 weeks in controlled environment chambers providing 36 (ambient) or 100 (elevated) Pa CO2. Averaged over all harvest dates above-ground biomass was greater (P < 0.05) in the elevated than in the ambient CO2 treatment but shoot biomass did not differ between treatments on the final harvest. Flowering was delayed by CO2 enrichment. One or more flowers were observed for 52% and 100% of the elevated and ambient CO2 grown plants, respectively, after 4-weeks growth. Starch and sucrose levels were increased 132 and 43%, respectively, in leaves of 6-week-old plants in response to CO2 enrichment. Nitrate varied with plant age, although mean nitrate levels in rosettes were decreased 31% by CO2 enrichment when averaged over all harvest dates. Chlorophyll, the chlorophyll a/b ratio, carotenoids and total soluble protein did not differ between CO2 treatments. Total Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity decreased with plant age and was lower (P < 0.01) in the elevated compared to the ambient CO2 treatment. The above results suggested that acclimation to elevated CO2 occurred in Arabidopsis without developing symptoms of N-deficiency. A total of 400 major proteins were separated and compared by two-dimensional gel electrophoresis. No proteins appeared de novo or disappeared in response to CO2 enrichment, although pixel densities for 13 protein spots differed significantly between CO2 treatments on at least one harvest date. Six of these proteins were identified by mass spectrometry. Three of these identified proteins were involved in plant growth and development or were associated with stress. Two other proteins were encoded by genes with putative functions. Only one protein, the 23 kD subunit of the oxygen evolving complex (OEC23), was involved in photosynthesis. It was concluded that long-term plant growth in elevated CO2 only caused small changes in the Arabidopsis proteome.