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Oxygen response of leaf CO2 compensation points used to determine Rubisco specificity factors of gymnosperm species.
Journal of Plant Research ( IF 2.8 ) Pub Date : 2020-02-11 , DOI: 10.1007/s10265-020-01169-0
Shin-Ichi Miyazawa 1 , Hiroyuki Tobita 2 , Tokuko Ujino-Ihara 1 , Yuji Suzuki 3
Affiliation  

Rubisco specificity factor (Sc/o), a measure of the relative capacities of an enzyme to catalyze carboxylation and oxygenation of ribulose-1,5-bisphosphate, determines the extent of photosynthetic CO2 assimilation and photorespiratory CO2 release. The current model of C3 photosynthesis, the Farquhar-von Caemmerer-Berry (FvCB) model, requires a species-specific Sc/o. However, Sc/o values have never been reported in conifers, likely because in vitro kinetic analysis of conifer Rubisco presents difficulties. To estimate the Sc/o of conifers and compare it with angiosperm Sc/o, we measured changes in leaf CO2 compensation points (Γ) in response to O2 partial pressure for a variety of leaves, with different rates of day respiration (Rday) and maximum Rubisco carboxylation (Vcmax) in gymnosperms (Ginkgo biloba), conifers (Metasequoia glyptostroboides and Cryptomeria japonica), and angiosperms (Nicotiana tabacum and Phaseolus vulgaris). As predicted by the FvCB model, the slope of a linear function of Γ vs O2 partial pressure, d, increased alongside increasing Rday/Vcmax. The Sc/o was obtainable from this relationship between d and Rday/Vcmax, because the d values at Rday/Vcmax = 0 corresponded to α/Sc/o, where α was the photorespiratory CO2 release rate per Rubisco oxygenation rate (generally assumed to be 0.5). The calculated Sc/o values of N. tabacum and P. vulgaris exhibited good agreement with those reported by in vitro studies. The Sc/o values of both conifers were similar to those of the two angiosperm species. In contrast, the Sc/o value of G. biloba was significantly lower than those of the other four studied species. These results suggest that our new method for Sc/o estimation is applicable to C3 plants, including those for which in vitro kinetic analysis is difficult. Furthermore, results also suggest that conifer Sc/o does not differ significantly from that of C3 angiosperms, assuming α remains unchanged.

中文翻译:

叶片CO2补偿点的氧气响应用于确定裸子植物物种的Rubisco特异性因子。

Rubisco特异性因子(Sc / o)是酶催化1,5-双磷酸核糖的羧化和氧合反应的相对能力的量度,它决定了光合CO2同化和光呼吸CO2释放的程度。当前的C3光合作用模型Farquhar-von Caemmerer-Berry(FvCB)模型需要特定于物种的Sc / o。但是,从未在针叶树中报道过Sc / o值,这可能是由于针叶树Rubisco的体外动力学分析存在困难。为了估算针叶树的Sc / o并将其与被子植物Sc / o进行比较,我们测量了不同日呼吸速率(Rday)和裸子植物(银杏叶)的最大Rubisco羧化(Vcmax),针叶树(Metasequoia glyptostroboides和Cryptomeria japonica)和被子植物(烟草(Nicotiana tabacum)和菜豆(Phaseolus vulgaris))。正如FvCB模型所预测的那样,Γ对O2分压d的线性函数的斜率随着Rday / Vcmax的增加而增加。从d与Rday / Vcmax之间的这种关系可以获得Sc / o,因为Rday / Vcmax = 0时的d值对应于α/ Sc / o,其中α是每Rubisco氧合速率的光呼吸CO2释放速率(通常假定为是0.5)。烟草和寻常型烟草的Sc / o值与体外研究报告的Sc / o值显示出良好的一致性。两个针叶树的Sc / o值与两个被子植物的Sc / o值相似。相反,银杏的Sc / o值明显低于其他四个研究物种的Sc / o值。这些结果表明我们的Sc / o估计新方法适用于C3植物,包括那些难以进行体外动力学分析的植物。此外,结果还表明,假设α保持不变,针叶树Sc / o与C3被子植物的差异不大。
更新日期:2020-02-11
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