Activity and activation state of ribulose-1,5-bisphosphate carboxylase of spruce trees with varying degrees of damage relative to the occurrence of novel forest decline

Rubisco, the primary carboxylating enzyme in photosynthesis, must be activated to catalyze CO2 fixation. The concept of an 'activase', a specific protein for activating Rubisco, was first introduced in 1985 based largely on biochemical and genetic studies of a high CO2-requiring mutant of Arabidopsis (Salvucci et al. (1985) Photosynth Res 7: 193-201). Over the past ten years, details about the occurrence, structure, and properties of Rubisco activase have been elucidated. However, the mechanism of action of Rubisco activase remains elusive. This review discusses the need for and function of Rubisco activase and summarizes information about the properties and structure of Rubisco activase. The information is evaluated in the context of the mechanism of Rubisco activase.

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The mechanism of Rubisco activase: Insights from studies of the properties and structure of the enzyme

Salvucci

Ogren

1996

Photosynth Res

148

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Ozone-induced microscopical changes and quantitative carbohydrate contents of hybrid poplar (Populus � euramericana)

Landolt

Günthardt‐Goerg

Pfenninger

et al. 1994

Trees

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Summary. Cuttings of hybrid poplar (Populus • euramericana var. "Dorskamp") were exposed to ozone (80 ]xg/m 3 from 2100 hours to 0700 hours, 180 [.tg/m 3 from 0700 hours to 2100 hours) for 3 months. Ozone reduced the starch content in leaves and stem bark, whereas starch granules accumulated in bundle sheath cells along small leaf veins. At the same time, sucrose and inositol content increased in the leaves. Mesophyll cells in the vicinity of the stomata were injured first, and droplet-like material appeared on their walls. In the sieve plates of fumigated trees, the pores showed a higher degree of narrowing than those of the control treatment. Cell collapse in the leaves was accompanied by water loss and an increase in air space. In the stems, the ozone treatment led to a reduced radial width, particularly in the xylem tissue. These results are discussed in relation to reduced or inhibited phloem loading and ozone-induced drought stress. The plants injured by ozone showed quite distinct patterns of metabolite responses as well as enzyme activities (PEP-and RubPcarboxylase) in the leaves from the top to the bottom. There were also remarkable differences in the reaction of sucrose and inositol between leaves and stem bark. Future research should therefore increasingly follow a whole-plant approach for a better understanding of complex plant reactions.

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The influence of ozone and nutrition on ?13C in Betula pendula

et al. 1995

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In the cellulose of stems and leaves, δC was investigated in a birch clone (Betula pendula), which was exposed throughout the growing season to either <3 (control) or 90/40 nl O 1 (day/night). Each regime was split into plants under high or low nutrient supply. δC was increased (becoming less negative), in stems rather than leaves, by both high nutrition (+2‰) and O stress (+1‰). Whereas high nutrition raised the wateruse efficiency (WUE) while lowering the CO concentration in the inner leaf air space (c ), WUE decreased and c increased under O stress. Therefore, only the nutritional effect on the carbon isotope fractionation was reproduced by the model of Farquhar et al. (1982) which estimates WUE by means of δC based on c . c was not biased by 'patchiness' in respect to stomatal opening. The latter was verified by microscopical analysis and the complete water infiltration of the birch leaves through the stomata, independent of the diurnal course of the leaf conductance for water vapour. Under low nutrient supply, the activity of phosphoenol pyruvate carboxylase (PEPC) was roughly doubled by ozone to about 1.3% of the total carboxylation capacity (by PEPC + rubisco), and was increased to 1.7% under high nutrition. The fractionation model, extended to account for varying activities of the carboxylating enzymes, indicated that stimulated PEPC was the cause of elevated δC, although c was increased under O stress. The stimulation of PEPC and, as a consequence, elevated δC are discussed as part of a whole-plant acclimation to O stress.

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Activity and activation state of ribulose-1,5-bisphosphate carboxylase of spruce trees with varying degrees of damage relative to the occurrence of novel forest decline

Cited by 15 publications

References 22 publications

The mechanism of Rubisco activase: Insights from studies of the properties and structure of the enzyme

The mechanism of Rubisco activase: Insights from studies of the properties and structure of the enzyme

Ozone-induced microscopical changes and quantitative carbohydrate contents of hybrid poplar (Populus � euramericana)

The influence of ozone and nutrition on ?13C in Betula pendula

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