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 (34) Citing Articles via Google Scholar Google Scholar Articles by Raghothama, K. G. Articles by Poovaiah, B. W. Search for Related Content PubMed PubMed Citation Articles by Raghothama, K. G. Articles by Poovaiah, B. W. Agricola Articles by Raghothama, K. G. Articles by Poovaiah, B. W.

Articles

Effect of Calmodulin Antagonists on Auxin-Induced Elongation ¹

Department of Horticulture and Landscape Architecture, Washington State University, Pullman, Washington 99164-6414

Coleoptile segments of oat (Avena sativa var Cayuse) and corn (Zea mays L. var Patriot) were incubated in different concentrations of calmodulin antagonists in the presence and absence of -naphthaleneacetic acid. The calmodulin antgonists (chlorpromazine (CP), trifluoperazine, and fluphenazine) inhibited the auxin-induced elongation at 5 to 50 micromolar concentrations. Chlorpromazine sulfoxide, an analog of chlorpromazine, did not have significant effect on the elongation of oat and corn coleoptiles. A specific inhibitor of calmodulin N-(6-aminohexyl)5-chloro-1-naphthalenesulfonamide hydrochloride (W-7, a naphthalenesulfonamide derivative) inhibited coleoptile elongation, while its inactive analog N-(6-aminohexyl)-1-naphthalenesulfonamide hydrochloride (W-5) was ineffective at similar concentrations. During a 4-hour incubation period, coleoptile segments accumulated significant quantities of ³H-CP. About 85 to 90% of auxin-induced growth was recovered after 4 hours of preincubation with CP or 12 hours with W-7 and transferring coleoptiles to buffer containing NAA. Leakage of amino acids from coleoptiles increased with increasing concentration of CP, showing a rapid and significant increase above 20 micromolar CP. The amount of amino acids released in the presence of W-7 and W-5 was significantly lower than the amount released in the presence of CP. Both W-5 and W-7 increased amino acid release but only W-7 inhibited auxin-induced growth. Calmodulin activity measured by phosphodiesterase activation did not differ significantly between auxin-treated and control coleoptile segments. These results suggest the possible involvement of calmodulin in auxin-induced coleoptile elongation.

¹ Scientific Paper No. 6801, College of Agriculture Research Center, Washington State University, Pullman, Project 0321. This work was supported in part by National Science Foundation Grant PCM-8208408 to B. W. P.

This article has been cited by other articles:

				T. Yang and B. W. Poovaiah Molecular and Biochemical Evidence for the Involvement of Calcium/Calmodulin in Auxin Action J. Biol. Chem., February 4, 2000; 275(5): 3137 - 3143. [Abstract] [Full Text] [PDF]