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. 1993 Jun;102(2):345–356. doi: 10.1104/pp.102.2.345

Mannose-6-Phosphate Reductase, a Key Enzyme in Photoassimilate Partitioning, Is Abundant and Located in the Cytosol of Photosynthetically Active Cells of Celery (Apium graveolens L.) Source Leaves.

J D Everard 1, V R Franceschi 1, W H Loescher 1
PMCID: PMC158787  PMID: 12231825

Abstract

Mannitol, a major photosynthetic product and transport carbohydrate in many plants, accounts for approximately 50% of the carbon fixed by celery (Apium graveolens L.) leaves. Previous subfractionation studies of celery leaves indicated that the enzymes for mannitol synthesis were located in the cytosol, but these data are inconsistent with that published for the sites of sugar alcohol synthesis in other families and taxa, including apple (Malus) and a brown alga (Fucus). Using antibodies to a key synthetic enzyme, NADPH-dependent mannose-6-phosphate reductase (M6PR), and immunocytochemical techniques, we have resolved both the inter-cellular and intracellular sites of mannitol synthesis. In leaves, M6PR was found only in cells containing ribulose-1,5-bisphosphate carboxylase/oxygenase. M6PR was almost exclusively cytosolic in these cells, with the nucleus being the only organelle to show labeling. The key step in transport carbohydrate biosynthesis that is catalyzed by M6PR displays no apparent preferential association with vascular tissues or with the bundle sheath. These results show that M6PR and, thus, mannitol synthesis are closely associated with the distribution of photosynthetic carbon metabolism in celery leaves. The principal role of M6PR is, therefore, in the assimilation of carbon being exported from the chloroplast, and it seems unlikely that this enzyme plays even an indirect role in phloem loading of mannitol.

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Selected References

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  1. Bradford M. M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 1976 May 7;72:248–254. doi: 10.1006/abio.1976.9999. [DOI] [PubMed] [Google Scholar]
  2. Brown R. H., Bouton J. H., Rigsby L., Rigler M. Photosynthesis of Grass Species Differing in Carbon Dioxide Fixation Pathways : VIII. Ultrastructural Characteristics of Panicum Species in the Laxa Group. Plant Physiol. 1983 Feb;71(2):425–431. doi: 10.1104/pp.71.2.425. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Burnette W. N. "Western blotting": electrophoretic transfer of proteins from sodium dodecyl sulfate--polyacrylamide gels to unmodified nitrocellulose and radiographic detection with antibody and radioiodinated protein A. Anal Biochem. 1981 Apr;112(2):195–203. doi: 10.1016/0003-2697(81)90281-5. [DOI] [PubMed] [Google Scholar]
  4. Davis J. M., Fellman J. K., Loescher W. H. Biosynthesis of Sucrose and Mannitol as a Function of Leaf Age in Celery (Apium graveolens L.). Plant Physiol. 1988 Jan;86(1):129–133. doi: 10.1104/pp.86.1.129. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Dingwall C., Laskey R. A. Protein import into the cell nucleus. Annu Rev Cell Biol. 1986;2:367–390. doi: 10.1146/annurev.cb.02.110186.002055. [DOI] [PubMed] [Google Scholar]
  6. Fink S. Some new methods for affixing sections to glass slides. I. Aqueous adhesives. Stain Technol. 1987 Jan;62(1):27–33. doi: 10.3109/10520298709107962. [DOI] [PubMed] [Google Scholar]
  7. Fox T. C., Kennedy R. A., Loescher W. H. Developmental Changes in Photosynthetic Gas Exchange in the Polyol-Synthesizing Species, Apium graveolens L. (Celery). Plant Physiol. 1986 Sep;82(1):307–311. doi: 10.1104/pp.82.1.307. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
  9. Negm F. B. Purification and Properties of an NADPH-Aldose Reductase (Aldehyde Reductase) from Euonymus japonica Leaves. Plant Physiol. 1986 Apr;80(4):972–977. doi: 10.1104/pp.80.4.972. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Restrepo M. A., Freed D. D., Carrington J. C. Nuclear transport of plant potyviral proteins. Plant Cell. 1990 Oct;2(10):987–998. doi: 10.1105/tpc.2.10.987. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Ried J. L., Walker-Simmons M. K., Everard J. D., Diani J. Production of polyclonal antibodies in rabbits is simplified using perforated plastic golf balls. Biotechniques. 1992 May;12(5):660–666. [PubMed] [Google Scholar]
  12. Robinson S. P., Walker D. A. The site of sucrose synthesis in isolated leaf protoplasts. FEBS Lett. 1979 Nov 15;107(2):295–299. doi: 10.1016/0014-5793(79)80394-4. [DOI] [PubMed] [Google Scholar]
  13. Rumpho M. E., Edwards G. E., Loescher W. H. A pathway for photosynthetic carbon flow to mannitol in celery leaves : activity and localization of key enzymes. Plant Physiol. 1983 Dec;73(4):869–873. doi: 10.1104/pp.73.4.869. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Usuda H., Edwards G. E. Localization of glycerate kinase and some enzymes for sucrose synthesis in c(3) and c(4) plants. Plant Physiol. 1980 May;65(5):1017–1022. doi: 10.1104/pp.65.5.1017. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Walker J. L., Oliver D. J. Glycine decarboxylase multienzyme complex. Purification and partial characterization from pea leaf mitochondria. J Biol Chem. 1986 Feb 15;261(5):2214–2221. [PubMed] [Google Scholar]
  16. Wang J. L., Klessig D. F., Berry J. O. Regulation of C4 Gene Expression in Developing Amaranth Leaves. Plant Cell. 1992 Feb;4(2):173–184. doi: 10.1105/tpc.4.2.173. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. van der Krol A. R., Chua N. H. The basic domain of plant B-ZIP proteins facilitates import of a reporter protein into plant nuclei. Plant Cell. 1991 Jul;3(7):667–675. doi: 10.1105/tpc.3.7.667. [DOI] [PMC free article] [PubMed] [Google Scholar]

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