Dim-Red-Light-Induced Increase in Polar Auxin Transport in
Cucumber Seedlings
: I. Development of Altered Capacity, Velocity, and Response to
Inhibitors |
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Authors: | James R. Shinkle Rajan Kadakia Alan M. Jones |
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Affiliation: | Department of Biology, Trinity University, San Antonio, Texas 78212–7200 (J.R.S., R.K.);Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599–3280 (A.M.J.) |
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Abstract: | We have developed and characterized a system to analyze light effects on auxin transport independent of photosynthetic effects. Polar transport of [3H]indole-3-acetic acid through hypocotyl segments from etiolated cucumber (Cucumis sativus L.) seedlings was increased in seedlings grown in dim-red light (DRL) (0.5 μmol m−2 s−1) relative to seedlings grown in darkness. Both transport velocity and transport intensity (export rate) were increased by at least a factor of 2. Tissue formed in DRL completely acquired the higher transport capacity within 50 h, but tissue already differentiated in darkness acquired only a partial increase in transport capacity within 50 h of DRL, indicating a developmental window for light induction of commitment to changes in auxin transport. This light-induced change probably manifests itself by alteration of function of the auxin efflux carrier, as revealed using specific transport inhibitors. Relative to dark controls, DRL-grown seedlings were differentially less sensitive to two inhibitors of polar auxin transport, N-(naphth-1-yl) phthalamic acid and 2,3,5-triiodobenzoic acid. On the basis of these data, we propose that the auxin efflux carrier is a key target of light regulation during photomorphogenesis. |
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