This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (20) Citing Articles via Google Scholar Google Scholar Articles by Ray, P. M. Search for Related Content PubMed PubMed Citation Articles by Ray, P. M. Agricola Articles by Ray, P. M.

Articles

Auxin and Fusicoccin Enhancement of -Glucan Synthase in Peas ¹

An Intracellular Enzyme Activity Apparently Modulated by Proton Extrusion

Department of Biological Sciences, Stanford University, Stanford, California 94305

Fusicoccin (FC), like indoleacetic acid (IAA), causes Golgi-localized -1,4-glucan synthase (GS) activity to increase when applied to pea third internode segments whose GS activity has declined after isolation from the plant. This suggests that GS activity is modulated by H⁺ extrusion; in agreement, vanadate and nigericin inhibit the GS response. The GS response is not due to acidification of the cell wall. Treatment of tissue with heavy water, which in effect raises intracellular pH, mimics the IAA/FC GS response. However, various treatments that tend to raise cytoplasmic pH directly, other than IAA- or FC-induced H⁺ extrusion, failed to increase GS activity, suggesting that cytoplasmic pH is not the link between H⁺ extrusion and increased GS activity. Although FC stimulates H⁺ extrusion more strongly than IAA does, FC enhances GS activity at most only as much as, and often somewhat less than, IAA does. This and other observations indicate that GS enhancement is probably not due to membrane hyperpolarization, stimulated sugar uptake, or changes in ATP level, but leave open the possibility that GS is controlled by H⁺ transport-driven changes in intracellular concentrations of ions other than H⁺.

This article has been cited by other articles:

				K. S. Dhugga, S. C. Tiwari, and P. M. Ray A reversibly glycosylated polypeptide (RGP1) possibly involved in plant cell wall synthesis: Purification, gene cloning, and trans-Golgi localization PNAS, July 8, 1997; 94(14): 7679 - 7684. [Abstract] [Full Text] [PDF]