Poster: Hormones
Abs #
648: Auxin transport and electric fields in Zea mayscoleoptiles
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Presenter: |
Johnson, Errin E, ejoh4660@mail.usyd.edu.au |
Authors | Johnson, Errin E (A) Overall, Robyn L (A) | | Affiliations: |
(A): School of Biological Sciences, The University of Sydney, NSW, Australia 2006
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Auxin, most abundant as indole-acetic acid (IAA), can be transported through the plant in a unique and tightly controlled manner. According to the chemiosmotic model, polar auxin transport relies on a pH gradient between the cell wall and cytoplasm, and on the asymmetric distribution of auxin efflux carrier proteins. However, it remains unclear how the specific position of these proteins on the plasma membrane is established. The present study investigated the hypothesis that endogenous electric fields direct the localisation of auxin transport proteins, by examining the effects of various pre-treatments to auxin transport in coleoptile segments of Zea mays. A positive electric field (1 hr, 1 Vcm-1) applied to the apical end of segments 6 hrs after excision significantly reduced the velocity of basipetal 3H-IAA transport, relative both to those exposed to a negative at apex field and to freshly excised segments. 3H-IAA uptake was not affected. It was proposed that during the 6 hr period prior to field application, the negatively charged efflux carriers became free to electrophorese from cell base to apex under the influence of a positive field, thereby reducing the rate that IAA is transported down cell files. Gravitropism and depletion of endogenous auxin were investigated as possible causes of this hypothesised efflux carrier redistribution. A similar decrease in 3H-IAA transport velocity was observed regardless of coleoptile orientation in the period prior to field application, but not in segments that had a continuous supply of auxin during this time. While the importance of endogenous electric fields in this context remains unclear, these results do support a role for an auxin gradient in the regulation of auxin transport protein distribution.
