PHOTOSYNTHESIS AND CARBOHYDRATE METABOLISM IN DETACHED LEAVES OF <i>LOLIUM TEMULENTUM</i> L.

Housley, T. L.; Pollock, C. J.

doi:10.1111/j.1469-8137.1985.tb03678.x

Cited by 94 publications

(59 citation statements)

References 19 publications

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“…3). This is in agreement with previous research that has reported a correlation between SST activity and the level of sucrose in the tissue (5,6,8,12,13,15). However, it remains unclear whether the product of photosynthesis that actually induces SST activity is sucrose and not one of its metabolites.…”

Section: Discussionsupporting

confidence: 82%

“…SST emerged as a key regulatory enzyme because SST activity and the rate of fructan synthesis were closely correlated under various conditions (1 1-13), and because SST activity increased rapidly upon feeding of sugars (14) or treatments that cause accumulation of photosynthate, such as illumination of excised leaves ( 13) or cold treatments (8,12), and decreased equally rapidly upon treatments lowering the photosynthate level (13). It has been suggested that a threshold level ofsucrose in the tissue is the key for induction of SST and fructan biosynthesis (5,6,13,15).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Regulation of Sucrose-Sucrose-Fructosyltransferase in Barley Leaves

Obenland

Simmen²,

Böller³

et al. 1991

Plant Physiol.

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The activity of sucrose-sucrose-fructosyltransferase (SST), a vacuolar enzyme strongly induced by light in excised leaves of barley (Hordeum vulgare L.), rapidly declined even in continuous light upon feeding of cycloheximide (CHI). The rate of decline was similar to that observed in light-treated leaves that were placed into darkness, in the presence or absence of CHI. The protease inhibitor leupeptin totally stopped the decline in SST activity in the dark and caused a substantial increase in the rate of induction of SST activity by light. Feeding of sucrose prevented or even reversed the SST activity decay induced by darkness in the absence of CHI but did not stabilize SST activity in the presence of CHI. The results suggest that SST is continuously subjected to rapid, constant proteolytic degradation in the vacuole, and that the enhancement of SST activity in the light or upon feeding sucrose in the dark is due exclusively to de novo protein synthesis.Fructans are polymers of fructose with a terminal glucose that function as major vacuolar storage carbohydrates in the vegetative organs of many important crop plants, most notably the forage grasses and cereals (9, 1 1). SST2, the first enzyme in the pathway of fructan synthesis, catalyzes the formation of the trisaccharide isokestose from two molecules of sucrose (9,11,14). The isokestose is then utilized by fructan-fructanfructosyltransferases to form fructans of varying degrees of polymerization.In previous work, barley leaves were used to study regulation of fructan biosynthesis. SST emerged as a key regulatory enzyme because SST activity and the rate of fructan synthesis were closely correlated under various conditions (1 1-13), and because SST activity increased rapidly upon feeding of sugars (14) or treatments that cause accumulation of photosynthate, such as illumination of excised leaves ( 13) or cold treatments (8,12), and decreased equally rapidly upon treatments lowering the photosynthate level (13). It has been suggested that a threshold level ofsucrose in the tissue is the key for induction of SST and fructan biosynthesis (5,6,13,15).Like the fructans, SST is localized in the vacuole (4, 12). The rapid changes in its activity are a paradigm of the dynam-' Supported by the Swiss National Science Foundation.2Abbreviations: SST, sucrose-sucrose-fructosyltransferase; CHI, cycloheximide.ics of the vacuole (2), but little is known about the regulatory mechanisms involved. Inhibitor studies have provided evidence that induction ofSST occurs at the level oftranscription and requires protein synthesis (3,13). However, the decay of SST activity is not affected by CHI, an inhibitor of protein synthesis, indicating that protein synthesis is not necessary for down-regulation of the enzyme (13).Here, we further exploit excised barley leaves as a model system and present evidence that SST is continuously degraded by leupeptin-sensitive proteinases. Regulation appears to occur exclusively by changes in the rate of its synthesis on the background of rapi...

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Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Regulation of Sucrose-Sucrose-Fructosyltransferase in Barley Leaves

Obenland

Simmen²,

Böller³

et al. 1991

Plant Physiol.

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“…One can be defined as specific 1-SST, because it forms practically only I-kestose and Glc from SUC. This enzyme is in a11 likelihood the same as the one previously characterized from barley protoplasts (Wagner and Wiemken, 1987), and it probably corresponds to the SST activities found in Lolium (Housley and Pollock, 1985;Cairns and Pollock, 1988) and in Agropyron (Chatterton et al, 1988). The other is a 6-SST that produces 6-kestose as the only trisaccharide but has some invertase activity.…”

Section: Enzymology Of Fructan Synthesismentioning

confidence: 61%

Fructan Synthesis in Excised Barley Leaves (Identification of Two Sucrose-Sucrose Fructosyltransferases Induced by Light and Their Separation from Constitutive Invertases)

Simmen¹,

Obenland²,

Boller³

et al. 1993

Plant Physiol.

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“…A decrease in the activity of this enzyme may be necessary if low temperature leads to increased storage of sucrose in the vacuole which would obviate osmotic problems imposed by high concentrations of cytoplasmic sucrose. The accumulation of sucrose in the vacuole could also serve to trigger fructan synthesis, even though the subsequent synthesis of fructan in the vacuole is predominantly from sucrose in the cytoplasm (Edelman & Jefford, 1968;Housley & Pollock, 1985). Although Al in the leaves is unlikely to be directly involved in the synthesis of the fructan precursor (Edelman & Jefford, 1968;Wagner, Keller & Wiemken, 1983), its role in the control of fructan synthesis on degradation has not been fully investigated.…”

Section: Discussionmentioning

confidence: 99%

THE INFLUENCE OF LOW TEMPERATURE ON DIEL PATTERNS OF CARBOHYDRATE METABOLISM IN LEAVES OF POA ANNUA L. AND POA×JEMTLANDICA (ALMQ.) RICHT.

Borland

Farrar

1987

New Phytologist

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SUMMARYThe effect of low temperature on diel changes in net gas exchange, carbohydrate content and export, and on the extractable activities of sucrose phosphate synthase and acid invertase from leaves of Poa annua (a ruderal grass) and Poa xjemtlandica (a subarctic grass) was investigated. Exposure for 5 d to a temperature of 7 °C significantly reduced the rate of net photosynthesis of P. annua but had no effect that of P. xjemtlandica. In both species, soluble sugars constituted 20 % of the dry weight and showed net accumulation over 24 h. There was approximately twice the concentration of fructans in the leaves of P. xjemtlandica compared with P. annua.During the 16 h photoperiod, the leaves of P. xjemtlandica stored twice as much photosynthate as the leaves of P. annua. However, the higher rate of export from the leaves of P. xjemtlandica in the dark compared to P. annua resulted in the allocation of similar proportions of photosynthate to the processes of storage, respiration and export in leaf blades of both species over a 24 h period.Low temperature resulted in a decrease in the extractable activity of sucrose phosphate synthase from P. annua but not from P. xjemtlandica. The activity of acid invertase was reduced by exposure in both species.

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PHOTOSYNTHESIS AND CARBOHYDRATE METABOLISM IN DETACHED LEAVES OF LOLIUM TEMULENTUM L.

Cited by 94 publications

References 19 publications

Regulation of Sucrose-Sucrose-Fructosyltransferase in Barley Leaves

Regulation of Sucrose-Sucrose-Fructosyltransferase in Barley Leaves

Fructan Synthesis in Excised Barley Leaves (Identification of Two Sucrose-Sucrose Fructosyltransferases Induced by Light and Their Separation from Constitutive Invertases)

THE INFLUENCE OF LOW TEMPERATURE ON DIEL PATTERNS OF CARBOHYDRATE METABOLISM IN LEAVES OF POA ANNUA L. AND POA×JEMTLANDICA (ALMQ.) RICHT.

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