Rubisco activase is a key regulator of non-steady-state photosynthesis at any leaf temperature and, to a lesser extent, of steady-state photosynthesis at high temperature
Article first published online: 6 JUL 2012
© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd
The Plant Journal
Volume 71, Issue 6, pages 871–880, September 2012
How to Cite
Yamori, W., Masumoto, C., Fukayama, H. and Makino, A. (2012), Rubisco activase is a key regulator of non-steady-state photosynthesis at any leaf temperature and, to a lesser extent, of steady-state photosynthesis at high temperature. The Plant Journal, 71: 871–880. doi: 10.1111/j.1365-313X.2012.05041.x
- Issue published online: 6 SEP 2012
- Article first published online: 6 JUL 2012
- Accepted manuscript online: 5 MAY 2012 11:06AM EST
- Received 21 March 2012; revised 16 April 2012; accepted 30 April 2012; published online 6 July 2012.
Table S1. CO2 compensation point was determined from A–Ci curves at several leaf temperatures. The catalytic turnover rate of Rubisco was calculated from CO2 assimilation rates at 250 µmol mol−1 CO2 concentration (A250) and carbamylated Rubisco content (μmol mol−1 s−1) at several leaf temperatures, according to Yamori and von Caemmerer (2009). Data represent means ± SE, n = 4–5.
Table S2. The relaxation time, which is an indication of the time required to complete activation of photosynthesis, at 15, 25 and 40°C. The relaxation time was calculated from the rate constant for photosynthetic induction, according to Woodrow and Mott (1989). Data represent means ± SE, n = 4–5. Different letters indicate significant differences in the photosynthetic components among WT, activase overexpressing plants and antisense plants at each leaf temperature (Tukey–Kramer multiple comparison test; P < 0.05).
Figure S1. CO2 assimilation rate at 390 µmol mol−1 CO2 concentration (A390), at 1200 µmol mol−1 CO2 concentration (A1200), and the Rubisco activation state at 390 µmol mol-1 CO2 concentration under 1500 µmol photons m−2 s−1 as a function of Rubisco activase content. A390, A1200 and Rubisco activation state at 390 µmol mol−1 CO2 concentration was shown at leaf temperatures of 15, 25 and 40 °C. Wild type: black circle, activase overexpressing plants: red triangle, antisense plants: blue diamond.
Figure S2. Temperature response of CO2 assimilation rate and the Rubisco activation state under 1500 µmol photons m−2 s−1at 250 or 390 µmol mol−1 CO2 concentration. Wild type: black circle, activase overexpressing plants: red triangle, antisense plants: blue diamond. Data represent means ± SE, n = 4–5.
Figure S3. Response of normalized CO2 assimilation rate (A) after an increase or decrease in light intensity at 15, 25 and 40 °C after a step increase or decrease in light intensity. To measure the response of photosynthesis at 250 μmol mol−1 CO2 concentration to an increased or decreased light intensity, plants were first allowed to reach a steady-state rate of photosynthesis at 1500 μmol m−2 s−1 for 30 min and were subsequently placed for 40 min at the initial low level of 60 μmol m−2 s−1. The leaves were then re-irradiated at a high light intensity of 1500 μmol m−2 s−1 and photosynthetic measurements were recorded. After the analysis of time course of photosynthetic activation, the leaves were again placed at the initial low level of 60 μmol m−2 s−1 and photosynthetic measurements were recorded. To remove the effects of changes in Ci, the photosynthesis rates were normalized to a Ci of 250 μmol mol−1 (Woodrow and Mot, 1989). These normalized data were plotted as the natural logarithm of the difference between the final stead-state rate (Af) and the rate (A) at each time point. The linear portion of the semi-logarithmic plot reflects an exponential phase vs time which is considered to be limited primarily by Rubisco (Woodrow and Mott, 1989). Therefore, the slope of the linear phase indicates an apparent rate constant for photosynthetic induction. Wild type: black circle, activase overexpressing plants: red triangle, antisense plants: blue diamond. Values are the mean; n = 4–5.
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