PLANT PHYSIOLOGY , Vol 110, Issue 4 1323-1328, Copyright © 1996 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Evidence That Zeaxanthin Is Not the Photoreceptor for Phototropism in Maize Coleoptiles
J. M. Palmer, KMF. Warpeha and W. R. Briggs
Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, Stanford, California 94305
The photoreceptor that mediates blue-light-induced phototropism in
dark-grown seedlings of higher plants has not been identified, although the
carotenoid zeaxanthin has recently been proposed as the putative
chromophore. In the experiments described in this paper, we analyzed
phototropism and a blue-light-induced protein phosphorylation that has been
genetically and physiologically implicated in phototropism in wild-type
maize (Zea mays L.) seedlings and compared the results with those from
seedlings that are either carotenoid deficient through a genetic lesion or
have been chemically treated to block carotenoid biosynthesis. The
blue-light-dependent phototropism and phosphorylation responses of
seedlings deficient in carotenoids are the same as those of seedlings
containing normal levels of carotenoids. These results and those in the
literature make it unlikely that zeaxanthin or any other carotenoid is the
chromophore of the blue-light photoreceptor for phototropism or the
blue-light-induced phosphorylation related to phototropism.
