The auxin-resistant diageotropica mutant of tomato responds to gravity via an auxin-mediated pathway |
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Authors: | Margaret S Rice Terri L Lomax |
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Institution: | (1) Department of Botany and Plant Pathology and Center for Gene Research and Biotechnology, Oregon State University, Corvallis, OR 97331-2902, USA, US |
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Abstract: | Hypocotyls of the diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) do not elongate in response to exogenous auxin, but can respond to gravity. This appears paradoxical in light of the
Cholodny-Went hypothesis, which states that shoot gravicurvature results from asymmetric stimulation of elongation by auxin.
While light-grown dgt seedlings can achieve correct gravitropic reorientation, the response is slow compared to wild-type seedlings. The sensitivity
of dgt seedlings to inhibition of gravicurvature by immersion in auxin or auxin-transport inhibitors is similar to that of wild-type
plants, indicating that both an auxin gradient and auxin transport are required for the gravitropic response and that auxin
uptake, efflux, and at least one auxin receptor are functional in dgt. Furthermore, dgt gravicurvature is the result of asymmetrically increased elongation as would be expected for an auxin-mediated response.
Our results suggest differences between elongation in response to exogenous auxin (absent in dgt) and elongation in response to gravistimulation (present but attenuated in dgt) and confirm the presence of two phases during the gravitropic response, both of which are dependent on functional auxin
transport.
Received: 16 July 1999 / Accepted: 24 September 1999 |
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Keywords: | : Auxin sensitivity – Auxin-transport inhibitors – Gravitropism – Hypocotyl elongation – Lycopersicon (mutant diageotropica) – Mutant (dgt tomato) |
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