Abstract
Comparing isolated plasma membrane vesicles and excised hypocotyl segments from etiolated seedlings of soybean [Glycine max (L.) Merr. cv. Williams], certain antiproliferative agents that inhibited growth inhibited plasma membrane redox activities. Additionally, auxins that stimulated growth stimulated plasma membrane redox activities. Hormone stimulation was restricted to NADH oxidase (determined from disappearance of NADH) and was given both by isolated plasma membranes and by a soluhilizedenzyme preparation. Comparing IAA, the native auxin regulator, and 2,4‐D, a synthetic regulator, stimulation was observed, hut the dose‐response curves were different. Yet, the dose‐response relationships of both stimulation of auxin growth and stimulation of NADH oxidase were parallel. Inhibition of auxin‐induced growth by antiproliferative drugs was more complex. Some, like actinomycin D, preferentially inhibited NADH oxidase (EC 1.6.99.2) but inhibited NADH‐ferricya‐nide oxido‐reductase (EC 1.6.99.3) as well. Others, like adriamycin, inhibited primarily the NADH‐ferricyanide oxido‐reductase. Therefore, growth control by auxin appeared to involve NADH oxidase as a rate‐limiting terminal oxidase to link electron flow from NADH to oxygen. This observation may provide a fundamental difference from animal cells. With the latter, impermeant electron acceptors such as diferric transferrin or ferricyanide fulfill such a role. In plants, these impermeant electron acceptors were without effect on growth or were growth inhibitory.
Published Version
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