Brown, Mia , Harrison, Marcia .
Ethylene Regulation of Gravitropic Curvature in Arabidopsis Stems.
Horizontal placement of a plant stem causes the redistribution of the soluble hormone auxin and stimulates biosynthesis of the gaseous hormone ethylene. While auxin is the primary plant hormone engaged in gravitropic responses through stimulation of growth, ethylene plays a modulating role in regulating the kinetics of this process. Ethylene is produced by the oxidation of 1-aminocyclopropane-1-carboxylic acid (ACC), which is formed from S-adenosyl methionine. The regulation of ACC synthesis by ACC synthase (ACS) serves as the rate-controlling step in ethylene biosynthesis. Our major research objective is to evaluate individual ACS forms in the regulation of gravitropism in dark-grown Arabidopsis seedlings. Potential changes in expression of the various ACS forms were evaluated in transgenic plants carrying ACS promoter-GUS fusions and by RT-PCR. Preliminary results do not reveal distinct changes in ACS expression within curving hypocotyls. The role of each ACS member in hypocotyl growth and gravitropic curvature was determined by comparing wild-type responses with those of mutants that do not express specific ACS forms. Compared to wild-type seedlings, mutants with increased ethylene of production (T-DNA insertion mutant of acs4, SALK_054951) showed significantly increased curvature by 7 hours after horizontal placement. Other acs mutants that did not exhibit increased ethylene production did not show changes in curvature kinetics. Overall, these results indicate a stimulatory role for ethylene in gravitropic curvature for Arabidopsis hypocotyls. (Supported by grants from the USDA National Research Initiative Competitive Grants Program, the American Society of Gravitational and Space Biology, and the WV Space Grant Consortium.).
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Marcia Harrison's webpage
1 - Marshall University, Integrated Science and Technology, One John Marshall Drive, Huntington, WV, 25755, USA
2 - Marshall University, Biological Sciences
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM