Differential effects of brefeldin A and cycloheximide on the activity of auxin efflux carriers in Cucurbita pepo L.

Robinson, J.S., Albert, A.C. and Morris, D.A. (1999) Differential effects of brefeldin A and cycloheximide on the activity of auxin efflux carriers in Cucurbita pepo L. Journal of Plant Physiology, 155 (6), 678-684.

Abstract

Brefeldin A (BFA), an inhibitor of Golgi-mediated protein traffic, stimulated net uptake of indole-3-acetic acid (IAA) by etiolated zucchini (Cucurbita pepo L.) hypocotyl tissue with a lag of less than 10 min, substantially reduced the rate of efflux of IAA from pre-loaded zucchini tissue, and strongly inhibited polar transport of IAA in zucchini hypocotyl and pea internode (Pisum sativum L.) segments. Pre-treatment of zucchini tissue with BFA (60 min), but not its simultaneous addition to the uptake medium, also greatly increased the FCCP-sensitive uptake of IAA by microsomal vesicles prepared from the pre-treated tissue. In contrast to the effects of BFA, application of the translation inhibitor cycloheximide (CH) did not affect any of the parameters of IAA transport investigated for at least 80 min and did not alter the responses to BFA. Nevertheless, CH rapidly (<10 min) reduced the incorporation of L-[35S]methionine into TCA-insoluble cell proteins and into microsomal membrane proteins. Together these results provide strong evidence that an essential protein component of the auxin efflux carrier system, targeted to the plasma membrane through the Golgi-mediated secretory system, turns over rapidly in the plasma membrane without a requirement for concurrent protein synthesis.

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