Yamori Wataru, Suzuki Kensaku, Noguchi Ko, Nakai Masato, Terashima Ichiro
Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Japan.
Plant Cell Environ. 2006 Aug;29(8):1659-70. doi: 10.1111/j.1365-3040.2006.01550.x.
Recently, several studies reported that the optimum temperature for the initial slope [IS(Ci)] of the light-saturated photosynthetic rate (A) versus intercellular CO2 concentration (Ci) curve changed, depending on the growth temperature. However, few studies compare IS(Ci) with ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) properties. Here, we assessed Rubisco activation state and in vitro Rubisco kinetics, the main determinants of IS(Ci), in spinach leaves grown at 30/25 [high temperature (HT)] and 15/10 degrees C [low temperature (LT)]. We measured Rubisco activation state and A at a CO2 concentration of 360 microL L(-1) (A360) at various temperatures. In both HT and LT leaves, the Rubisco activation state decreased with increasing temperatures above the optimum temperatures for A360, while the activation state remained high at lower temperatures. To compare Rubisco characteristics, temperature dependences of the maximum rate of ribulose 1,5-bisphosphate (RuBP) carboxylation (Vcmax), specificity factor (Sc/o) and thermal stability were examined. We also examined Vcmax, and thermal stability in the leaves that were transferred from HT to LT conditions and were subsequently kept under LT conditions for 2 weeks (HL). Rubisco purified from HT, LT and HL leaves are called HT, LT and HL Rubisco, respectively. Thermal stabilities of LT and HL Rubisco were similar and lower than that of HT Rubisco. Both Vcmax and Sc/o in LT Rubisco were higher than those of HT Rubisco at low temperatures, while these were lower at high temperatures. Vcmax in HL Rubisco were similar to those of LT Rubisco at low temperatures, and to those of HT Rubisco at high temperatures. The predicted photosynthetic rates, taking account of the Rubisco kinetics and the Rubisco activation state, agreed well with A360 in both HT and LT leaves. This study suggests that photosynthetic performance is largely determined by the Rubisco kinetics at low temperature and by Rubisco Kinetics and the Rubisco activation state at high temperature.
最近，多项研究报告称，光饱和光合速率（A）与细胞间二氧化碳浓度（Ci）曲线的初始斜率[IS（Ci）]的最佳温度会因生长温度而异。然而，很少有研究将IS（Ci）与1,5-二磷酸核酮糖羧化酶/加氧酶（Rubisco）的特性进行比较。在此，我们评估了在30/25 [高温（HT）]和15/10摄氏度[低温（LT）]下生长的菠菜叶片中Rubisco的活化状态和体外Rubisco动力学，这是IS（Ci）的主要决定因素。我们在不同温度下测量了二氧化碳浓度为360 μL L⁻¹时的Rubisco活化状态和A（A360）。在HT和LT叶片中，高于A360的最佳温度时，Rubisco活化状态随温度升高而降低，而在较低温度下活化状态保持较高。为了比较Rubisco的特性，研究了1,5-二磷酸核酮糖（RuBP）羧化最大速率（Vcmax）、特异性因子（Sc/o）和热稳定性的温度依赖性。我们还研究了从HT转移到LT条件并随后在LT条件下保持2周的叶片（HL）中的Vcmax和热稳定性。从HT、LT和HL叶片中纯化的Rubisco分别称为HT、LT和HL Rubisco。LT和HL Rubisco的热稳定性相似且低于HT Rubisco。在低温下，LT Rubisco的Vcmax和Sc/o均高于HT Rubisco，而在高温下则较低。HL Rubisco在低温下的Vcmax与LT Rubisco相似，在高温下与HT Rubisco相似。考虑到Rubisco动力学和Rubisco活化状态预测的光合速率与HT和LT叶片中的A360吻合良好。这项研究表明，光合性能在很大程度上由低温下的Rubisco动力学以及高温下的Rubisco动力学和Rubisco活化状态决定。
