Oxygen response of leaf CO2 compensation points used to determine Rubisco specificity factors of gymnosperm species
Autor: | Yuji Suzuki, Tokuko Ujino-Ihara, Hiroyuki Tobita, Shin-Ichi Miyazawa |
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Rok vydání: | 2020 |
Předmět: |
0106 biological sciences
0301 basic medicine biology Specificity factor Nicotiana tabacum RuBisCO Cryptomeria Plant Science biology.organism_classification Photosynthesis 01 natural sciences 03 medical and health sciences 030104 developmental biology Gymnosperm Carboxylation Botany biology.protein Phaseolus 010606 plant biology & botany |
Zdroj: | Journal of Plant Research. 133:205-215 |
ISSN: | 1618-0860 0918-9440 |
Popis: | 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. |
Databáze: | OpenAIRE |
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