Glycine as a substrate for photorespiration1

Kisaki, Takuro; Tolbert, N. E.

doi:10.1093/oxfordjournals.pcp.a074506

Cited by 67 publications

(28 citation statements)

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“…Some investigators believe that glyoxylate must first be converted to glycine, and that the CO2 in photorespiration is produced during the complex reaction by which two glycine molecules condense to produce serine, as shown in Fig. 2 (32, 33). Recent experiments comparing tissues supplied with [1-_4C]glycolate and [1-'4C]glycine suggest that the condensation of glycine to serine does not produce sufficient C02 to account for photorespiratory rates (34), and that a direct photooxidative decarboxylation of glyoxylate (Fig.…”

Section: Glycolate Biosynthesis and Photorespirationmentioning

confidence: 99%

Plant Productivity and the Control of Photorespiration

Zelitch

1973

Proc. Natl. Acad. Sci. U.S.A.

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The Green Revolution of the last decade has seen the yield of some food crops at least doubled by genetic alterations of plant stature and the ability of plants to respond to increased fertilizer. Since only 5-10% of the dry weight of plants comes from minerals and nitrogen in the soil, it is becoming more difficult to obtain further increases in productivity by this approach. Even scientists associated with the Green Revolution believe they have reached a plateau by these methods (1). Therefore, the next large increases in productivity must come from increasing the 90-95% of the dry weight that comes from the assimilation of airborne CO2 during photosynthesis.The productivity of plants (dry weight per unit of ground area) is determined by the gross CO2 assimilation during photosynthesis minus the CO2 released during respiration. The "dark" respiration processes of green plants, which probably also occur as well in the light, are biochemically similar to those found in animal tissues and many microorganisms, and are essential for the growth and maintenance of plant cells. It is not certain whether all of the dark respiration is essential, or whether some portion of it may sometimes be uncoupled from ATP production. This wasteful portion of respiration could cause diminished productivity (2). However, it is well documented that many plant species and varieties respire away large portions of their recently fixed CO2 during illumination by an entirely different biochemical process of respiration, known as photorespiration. Since photorespiration is often much faster in terms of CO2 production than dark respiration, photorespiration greatly lowers plant productivity where this occurs. Some biochemical and plant breeding experiments will be described that hold promise for retention of much of the photorespired C02, leading to large increases in crop yields.Relation of net photosynthesis to productivity among speciesCrop species vary greatly in their yields of dry weight. For example, from statistics of average market yield in the United States (Table 1), one can calculate that the crop growth rate for maize silage, sorghum silage, and sugarcane (cane) is at least double that for spinach, tobacco (leaf plus stalk), and hay grasses (3). The higher-yielding leafy species all have low fluxes of photorespiration compared with the less efficient species. Table 2 contains typical values of CO2 assimilation taken from the literature; it shows that much faster rates are usually found in the higher-yielding tropical grasses and in some weeds, as compared with many common crop plantsincluding spinach, tobacco, and orchard grass-that are lower yielding. A large part of the differences in net photosynthesis between the efficient and nonefficient species can be explained by the much slower rate of photorespiration that is encountered naturally only in the efficient plants. Characteristics of photorespirationSince photorespiration is such an important process, it is interesting to speculate on why its discovery was so long delayed....

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Section: Glycolate Biosynthesis and Photorespirationmentioning

confidence: 99%

Plant Productivity and the Control of Photorespiration

Zelitch

1973

Proc. Natl. Acad. Sci. U.S.A.

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“…The high affinity for CO2 in maize leaves could be caused by the nature of the irreversible reaction which is involved in feeding the CO2 reserve (24,27). Thus a possible explanation of the low compensation point found in maize (10,23,30) …”

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Studies on the Mechanism of Glycerate 3-Phosphate Synthesis in Tomato and Maize Leaves

Galmiche¹

1973

Plant Physiol.

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The net carbon incorporation in maize (Zea mays) and tomato (Lycopersicum esculentum) leaves was mainly the result of the carboxylation of ribulose 1,5-diphosphate. (20,28) as in the Calvin-type plants (C3 plants). This proposition is supported by enzymic studies (2,8,9,11,35) and the changes in reservoir sizes of RuDP following a CO2 pressure decrease (14, 28). Conflicting results are reported on the location of RuDP and PEP carboxylases in C4 plants (7-9, 12, 36, 37). Wherever the RuDP and PEP carboxylation may be operating in these C4 plants the general scheme is the following. CO2 is first incorporated in C4-dicarboxylic acid and then into PGA by RuDP carboxylase (3).In both types of plants RuDP carboxylation is a key reaction. Nevertheless the RuDP carboxylase activity in tissue extracts of the C2 plants is apparently inadequate to account for

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“…Serine was the most labelled amino acid in the light, and was not derived from phosphoglyceric acid synthesized from respired COa (Table 6). Hence, part of the glucose may enter into the photosynthetic carbon reduction cycle within the chloroplasts, and subsequently be converted to glycollate there, followed by serine formation through the glycollate pathway (photorespiratory pathway) under light in peroxisomes and mitochondria ( 15,16,23), CooMBS and WliiTTINGHAM ( 7) showed that exogenous glucose was converted to glycollate in Chiarella in the light. It is, however, undeniable that part of the serine may be synthesized from some precursors produced in glycolysis.…”

Section: Discussionmentioning

confidence: 99%