Starch synthesis in amyloplasts purified from developing potato tubers

Naeem, Muhammad; Tetlow, Ian J.; Emes, Michael J.

doi:10.1046/j.1365-313x.1997.11051095.x

Cited by 66 publications

(35 citation statements)

References 27 publications

(55 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1c) (Pozueta-Romero et al 1991, Naeem et al 1997, Shannon et al 1998. Essentially in line with previous investigations describing the occurrence of cyclic gluconeogenic processes in bacteria (Gaudet et al 1992, Belanger and Hatfull 1999, Guedon et al 2000 and animals (David et al 1990, Massillon et al 1995, Bollen et al 1998 in which glycogen synthesis and degradation take place simultaneously, active turnover of starch has been shown to occur in non-photosynthetic tissues of plants (Pozueta-Romero and Akazawa 1993, Neuhaus et al 1995, Sweetlove et al 1996b.…”

Section: Introductionsupporting

confidence: 72%

Sucrose Synthase Catalyzes the de novo Production of ADPglucose Linked to Starch Biosynthesis in Heterotrophic Tissues of Plants

Baroja‐Fernández

Muñoz

Saikusa

et al. 2003

Plant and Cell Physiology

130

View full text Add to dashboard Cite

;By using barley seeds, developmental changes of ADPglucose (ADPG)-producing sucrose synthase (SS) and ADPG pyrophosphorylase (AGPase) have been compared with those of UDPglucose (UDPG), ADPG, sucrose (Suc) and starch contents. Both ADPG-synthesizing SS and AGPase activity patterns were found to correlate well with those of ADPG and starch contents. Remarkably, however, maximal activities of ADPG-synthesizing SS were found to be several fold higher than those of AGPase throughout seed development, the highest rate of starch accumulation being well accounted for by SS. Kinetic analyses of SS from barley endosperms and potato tubers in the Suc cleavage direction showed similar K m values for ADP and UDP, whereas apparent affinity for Suc was shown to be higher in the presence of UDP than with ADP. Moreover, measurements of transglucosylation activities in starch granules incubated with purified SS, ADP and [U-14 C]Suc revealed a low inhibitory effect of UDP. The ADPG and UDPG contents in the transgenic S-112 SS and starch deficient potato mutant [Zrenner et al. (1995) Plant J. 7: 97] were found to be 35% and 30% of those measured in wild-type plants, whereas both glucose-1-phosphate and glucose-6-phosphate contents were found to be normal as compared with those of wild-type plants. The overall results thus strongly support a novel gluconeogenic mechanism reported previously [Pozueta-Romero et al. (1999) Crit. Rev. Plant Sci. 18: 489] wherein SS catalyses directly the de novo production of ADPG linked to starch biosynthesis in heterotrophic tissues of plants.

show abstract

Section: Introductionsupporting

confidence: 72%

Sucrose Synthase Catalyzes the de novo Production of ADPglucose Linked to Starch Biosynthesis in Heterotrophic Tissues of Plants

Baroja‐Fernández

Muñoz

Saikusa

et al. 2003

Plant and Cell Physiology

130

View full text Add to dashboard Cite

show abstract

“…This raises the question whether or not Glc-1-P directly enters the chloroplasts where the starch synthesis takes place. Until now, Glc-1-P has not been reported to be imported into chloroplasts, but indirect evidence for an uptake by nongreen plastids has been published (for potato tubers, Kosegarten and Mengel, 1994;Naeem et al, 1997; for wheat [Triticum aestivum], Tetlow et al, 1996; for soybean [Glycine max], Coates and ap Rees, 1994). To answer the question mentioned above, chloroplasts isolated from Arabidopsis leaves were incubated with [U-14 C]Glc-1-P. As a control, an aliquot of the same chloroplast preparation was mechanically broken by using a potter and, subsequently, the homogenate was treated identically.…”

Section: Utilization Of External Glc-1-p By Isolated Arabidopsis Chlomentioning

confidence: 99%

Glucose-1-Phosphate Transport into Protoplasts and Chloroplasts from Leaves of Arabidopsis

et al. 2010

View full text Add to dashboard Cite

Almost all glucosyl transfer reactions rely on glucose-1-phosphate (Glc-1-P) that either immediately acts as glucosyl donor or as substrate for the synthesis of the more widely used Glc dinucleotides, ADPglucose or UDPglucose. In this communication, we have analyzed two Glc-1-P-related processes: the carbon flux from externally supplied Glc-1-P to starch by either mesophyll protoplasts or intact chloroplasts from Arabidopsis (Arabidopsis thaliana). When intact protoplasts or chloroplasts are incubated with [U-14C]Glc-1-P, starch is rapidly labeled. Incorporation into starch is unaffected by the addition of unlabeled Glc-6-P or Glc, indicating a selective flux from Glc-1-P to starch. However, illuminated protoplasts incorporate less 14C into starch when unlabeled bicarbonate is supplied in addition to the 14C-labeled Glc-1-P. Mesophyll protoplasts incubated with [U-14C]Glc-1-P incorporate 14C into the plastidial pool of adenosine diphosphoglucose. Protoplasts prepared from leaves of mutants of Arabidopsis that lack either the plastidial phosphorylase or the phosphoglucomutase isozyme incorporate 14C derived from external Glc-1-P into starch, but incorporation into starch is insignificant when protoplasts from a mutant possessing a highly reduced ADPglucose pyrophosphorylase activity are studied. Thus, the path of assimilatory starch biosynthesis initiated by extraplastidial Glc-1-P leads to the plastidial pool of adenosine diphosphoglucose, and at this intermediate it is fused with the Calvin cycle-driven route. Mutants lacking the plastidial phosphoglucomutase contain a small yet significant amount of transitory starch.

show abstract

“…The import of Glc-1-P into intact amyloplasts isolated from tubers or suspension-cultured cells from potato has been reported (Kosegarten and Mengel, 1994;Naeem et al, 1997), but the uptake of this sugar phosphate by intact cells has not been demonstrated so far. To gain further insight into this uptake process, 14 C-labeling experiments were performed with tuber discs that were incubated with several 14 C-labeled sugars or sugar derivatives, such as Suc, Glc, or Glc-1-P, both in the presence and absence of unlabeled sugar compounds (Fig.…”

Section: Selective Uptake Of Glc-1-p By Tuber Discsmentioning

confidence: 99%

Alterations in Cytosolic Glucose-Phosphate Metabolism Affect Structural Features and Biochemical Properties of Starch-Related Heteroglycans

et al. 2008

View full text Add to dashboard Cite

The cytosolic pools of glucose-1-phosphate (Glc-1-P) and glucose-6-phosphate are essential intermediates in several biosynthetic paths, including the formation of sucrose and cell wall constituents, and they are also linked to the cytosolic starch-related heteroglycans. In this work, structural features and biochemical properties of starch-related heteroglycans were analyzed as affected by the cytosolic glucose monophosphate metabolism using both source and sink organs from wild-type and various transgenic potato (Solanum tuberosum) plants. In leaves, increased levels of the cytosolic phosphoglucomutase (cPGM) did affect the cytosolic heteroglycans, as both the glucosyl content and the size distribution were diminished. By contrast, underexpression of cPGM resulted in an unchanged size distribution and an unaltered or even increased glucosyl content of the heteroglycans. Heteroglycans prepared from potato tubers were found to be similar to those from leaves but were not significantly affected by the level of cPGM activity. However, external glucose or Glc-1-P exerted entirely different effects on the cytosolic heteroglycans when added to tuber discs. Glucose was directed mainly toward starch and cell wall material, but incorporation into the constituents of the cytosolic heteroglycans was very low and roughly reflected the relative monomeric abundance. By contrast, Glc-1-P was selectively taken up by the tuber discs and resulted in a fast increase in the glucosyl content of the heteroglycans that quantitatively reflected the level of the cytosolic phosphorylase activity. Based on 14 C labeling experiments, we propose that in the cytosol, glucose and Glc-1-P are metabolized by largely separated paths.

show abstract

Starch synthesis in amyloplasts purified from developing potato tubers

Cited by 66 publications

References 27 publications

Sucrose Synthase Catalyzes the de novo Production of ADPglucose Linked to Starch Biosynthesis in Heterotrophic Tissues of Plants

Sucrose Synthase Catalyzes the de novo Production of ADPglucose Linked to Starch Biosynthesis in Heterotrophic Tissues of Plants

Glucose-1-Phosphate Transport into Protoplasts and Chloroplasts from Leaves of Arabidopsis

Alterations in Cytosolic Glucose-Phosphate Metabolism Affect Structural Features and Biochemical Properties of Starch-Related Heteroglycans

Contact Info

Product

Resources

About