The Regulation of Rubisco Activity in Response to Variation in Temperature and Atmospheric CO2 Partial Pressure in Sweet Potato

Abstract

The temperature response of net CO 2 assimilation rate (A), the rate of whole-chain electron transport, the activity and activation state of Rubisco, and the pool sizes of ribulose-1,5-bisphosphate (RuBP) and 3-phosphoglyceric acid (PGA) were assessed in sweet potato (Ipomoea batatas) grown under greenhouse conditions. Above the thermal optimum of photosynthesis, the activation state of Rubisco declined with increasing temperature. Doubling CO 2 above 370 mbar further reduced the activation state, while reducing CO 2 by one-half increased it. At cool temperature (,16°C), the activation state of Rubisco declined at CO 2 levels where photosynthesis was unaffected by a 90% reduction in O 2 content. Reduction of the partial pressure of CO 2 at cool temperature also enhanced the activation state of Rubisco. The rate of electron transport showed a pronounced temperature response with the same temperature optimum as A at elevated CO 2 . RuBP pool size and the RuBPto-PGA ratio declined with increasing temperature. Increasing CO 2 also reduced the RuBP pool size. These results are consistent with the hypothesis that the reduction in the activation state of Rubisco at high and low temperature is a regulated response to a limitation in one of the processes contributing to the rate of RuBP regeneration. To further evaluate this possibility, we used measured estimates of Rubisco capacity, electron transport capacity, and the inorganic phosphate regeneration capacity to model the response of A to temperature. At elevated CO 2 , the activation state of Rubisco declined at high temperatures where electron transport capacity was predicted to be limiting, and at cooler temperatures where the inorganic phosphate regeneration capacity was limiting. At low CO 2 , where Rubisco capacity was predicted to limit photosynthesis, full activation of Rubisco was observed at all measurement temperatures.

The Costs of Photorespiration to Food Production Now and in the Future

“…Rubisco content and expression in major C 3 crops decreases when plants are grown under elevated carbon dioxide (8,23,54,63). Additionally, the carbon dioxide level can affect how much of the Rubisco is active: The activation state of Rubisco decreased with carbon dioxide concentration in sweet potato (19). The activation state also decreased with temperature above the thermal optimum at each measurement of carbon dioxide concentration in these experiments, likely because of the limited thermotolerance of Rubisco activase, a vital chaperone for Rubisco activity (66).…”

Effect of Maize (Zea mays L.) Plant-Type on Yield and Photosynthetic Characters of Sweet Potato (Ipomoea balatas L.) in Intercropping System

“…As has been stated, RuBisCO activity is decreased with Ci within limited temperature of 0 to 30 °C (Cen and Sage, 2005). Sun is the direct source of crop light and heat.…”

Photosynthesis of Sago Palm (Metroxylon sagu Rottb.) Seedling at Different Air Temperatures

“…Low rubisco activity at 25 • C might be due to the reduction in RuBP regeneration [7,25]. RuBP regeneration might be affected by the lower RuBP consumption by rubisco.…”