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. 1999 Jan;11(1):127–140. doi: 10.1105/tpc.11.1.127

Translocation of structural P proteins in the phloem.

B Golecki 1, A Schulz 1, G A Thompson 1
PMCID: PMC144095  PMID: 9878637

Abstract

Phloem-specific proteins (P proteins) are particularly useful markers to investigate long-distance trafficking of macromolecules in plants. In this study, genus-specific molecular probes were used in combination with intergeneric grafts to reveal the presence of a pool of translocatable P protein subunits. Immunoblot analyses demonstrated that Cucurbita spp P proteins PP1 and PP2 are translocated from Cucurbita maxima stocks and accumulate in Cucumis sativus scions. Cucurbita maxima or Cucurbita ficifolia PP1 and PP2 mRNAs were not detected in Cucumis sativus scions by either RNA gel blot analysis or reverse transcription-polymerase chain reaction, indicating that the proteins, rather than transcripts, are translocated. Tissue prints of the Cucumis sativus scion, using antibodies raised against Cucurbita maxima PP1 or PP2, detected both proteins in the fascicular phloem of the stem at points distal to the graft union and in the petiole of a developing leaf, suggesting that the proteins move within the assimilate stream toward sink tissues. Cucurbita maxima PP1 was immunolocalized by light microscopy in sieve elements of the extrafascicular phloem of Cucumis sativus scions, whereas Cucurbita maxima PP2 was detected in both sieve elements and companion cells.

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Selected References

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  1. Allen A. K. A lectin from the exudate of the fruit of the vegetable marrow (Cucurbita pepo) that has a specificity for beta-1,4-linked N-acetylglucosamine oligosaccharides. Biochem J. 1979 Oct 1;183(1):133–137. doi: 10.1042/bj1830133. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Alosi M. C., Melroy D. L., Park R. B. The regulation of gelation of Phloem exudate from cucurbita fruit by dilution, glutathione, and glutathione reductase. Plant Physiol. 1988 Apr;86(4):1089–1094. doi: 10.1104/pp.86.4.1089. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Anantharam V., Patanjali S. R., Swamy M. J., Sanadi A. R., Goldstein I. J., Surolia A. Isolation, macromolecular properties, and combining site of a chito-oligosaccharide-specific lectin from the exudate of ridge gourd (Luffa acutangula). J Biol Chem. 1986 Nov 5;261(31):14621–14627. [PubMed] [Google Scholar]
  4. Balachandran S., Xiang Y., Schobert C., Thompson G. A., Lucas W. J. Phloem sap proteins from Cucurbita maxima and Ricinus communis have the capacity to traffic cell to cell through plasmodesmata. Proc Natl Acad Sci U S A. 1997 Dec 9;94(25):14150–14155. doi: 10.1073/pnas.94.25.14150. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Bostwick D. E., Dannenhoffer J. M., Skaggs M. I., Lister R. M., Larkins B. A., Thompson G. A. Pumpkin phloem lectin genes are specifically expressed in companion cells. Plant Cell. 1992 Dec;4(12):1539–1548. doi: 10.1105/tpc.4.12.1539. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Bostwick D. E., Skaggs M. I., Thompson G. A. Organization and characterization of Cucurbita phloem lectin genes. Plant Mol Biol. 1994 Nov;26(3):887–897. doi: 10.1007/BF00028856. [DOI] [PubMed] [Google Scholar]
  7. Clark A. M., Jacobsen K. R., Bostwick D. E., Dannenhoffer J. M., Skaggs M. I., Thompson G. A. Molecular characterization of a phloem-specific gene encoding the filament protein, phloem protein 1 (PP1), from Cucurbita maxima. Plant J. 1997 Jul;12(1):49–61. doi: 10.1046/j.1365-313x.1997.12010049.x. [DOI] [PubMed] [Google Scholar]
  8. Crafts A. S. PHLOEM ANATOMY, EXUDATION, AND TRANSPORT OF ORGANIC NUTRIENTS IN CUCURBITS. Plant Physiol. 1932 Apr;7(2):i4–225. doi: 10.1104/pp.7.2.183. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Cruz SS, Roberts AG, Prior DA, Chapman S, Oparka KJ. Cell-to-cell and phloem-mediated transport of potato virus X. The role of virions . Plant Cell. 1998 Apr;10(4):495–510. doi: 10.1105/tpc.10.4.495. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Esau K., Cronshaw J. Tubular components in cells of healthy and tobacco mosaic virus-infected Nicotiana. Virology. 1967 Sep;33(1):26–35. doi: 10.1016/0042-6822(67)90090-6. [DOI] [PubMed] [Google Scholar]
  11. Fisher D. B., Wu Y., Ku M. S. Turnover of soluble proteins in the wheat sieve tube. Plant Physiol. 1992 Nov;100(3):1433–1441. doi: 10.1104/pp.100.3.1433. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Gustincich S., Manfioletti G., Del Sal G., Schneider C., Carninci P. A fast method for high-quality genomic DNA extraction from whole human blood. Biotechniques. 1991 Sep;11(3):298-300, 302. [PubMed] [Google Scholar]
  13. Kühn C., Franceschi V. R., Schulz A., Lemoine R., Frommer W. B. Macromolecular trafficking indicated by localization and turnover of sucrose transporters in enucleate sieve elements. Science. 1997 Feb 28;275(5304):1298–1300. doi: 10.1126/science.275.5304.1298. [DOI] [PubMed] [Google Scholar]
  14. LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
  15. 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]
  18. Read S. M., Northcote D. H. Subunit structure and interactions of the phloem proteins of Cucurbita maxima (pumpkin). Eur J Biochem. 1983 Aug 15;134(3):561–569. doi: 10.1111/j.1432-1033.1983.tb07603.x. [DOI] [PubMed] [Google Scholar]
  19. Roberts A. G., Cruz S. S., Roberts I. M., Prior DAM., Turgeon R., Oparka K. J. Phloem Unloading in Sink Leaves of Nicotiana benthamiana: Comparison of a Fluorescent Solute with a Fluorescent Virus. Plant Cell. 1997 Aug;9(8):1381–1396. doi: 10.1105/tpc.9.8.1381. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Schaller A., Ryan C. A. Systemin--a polypeptide defense signal in plants. Bioessays. 1996 Jan;18(1):27–33. doi: 10.1002/bies.950180108. [DOI] [PubMed] [Google Scholar]
  21. Towbin H., Staehelin T., Gordon J. Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc Natl Acad Sci U S A. 1979 Sep;76(9):4350–4354. doi: 10.1073/pnas.76.9.4350. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Wolf S., Deom C. M., Beachy R. N., Lucas W. J. Movement protein of tobacco mosaic virus modifies plasmodesmatal size exclusion limit. Science. 1989 Oct 20;246(4928):377–379. doi: 10.1126/science.246.4928.377. [DOI] [PubMed] [Google Scholar]

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