Expression of the Auxin-Inducible GH3 Promoter/GUS Fusion Gene as a Useful Molecular Marker for Auxin Physiology |
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Authors: | Li, Yi Wu, Yan H. Hagen, Gretchen Guilfoyle, Tom |
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Affiliation: | 2 Department of Plant Science, U-67, University of Connecticut Storrs, CT 06269, U.S.A. 3 Department of Biochemistry, University of Missouri Columbia, MO 65211, U.S.A. |
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Abstract: | Expression of the GH3 promoter/GUS reporter (GH3/GUS) gene intransgenic tobacco is silent in most vegetative tissues andorgans, but can be specifically induced by auxin in all celltypes throughout the plant, indicating that auxin is a limitingfactor for activation of the GH3/GUS gene. In the absence ofexogenous auxin, expression of the GH3/GUS gene either correlateswith physiological events which are presumably mediated by auxinor occurs in cells where relatively high levels of endogenousauxin are expected. For example, the GH3/GUS gene is expressedin dormant lateral buds, tips of adventitious roots, and stemparenchyma cells where adventitious roots are initiating. TheGH3/GUS gene is activated at the cut surface nearest the tipof a leaf from which a strip of tissue has been excised, andin the basal end of an excised shoot segment. Also, the GH3/GUSgene is expressed predominantly in the lower side of a gravistimulatedshoot and in the dark side of a unilateral light-stimulatedshoot. Furthermore, the expression pattern of the GH3/GUS geneis similar to the distribution pattern of 14C-IAA that is appliedat the apical end of the gravistimulated shoot. Thus, the resultsreported here provide additional support for a crucial roleof auxin in shoot gravi- and photo-tropisms and adventitiousroot formation. Furthermore, the data presented in this reportalso indicate that expression of the GH3/GUS gene is an excellentmolecular marker for studying auxin transport and for monitoringchanges in either auxin concentration or cellular sensitivityto auxin in planta. 1 This work was supported by NASA grant NAG10-0189 and a subgrantof NASA NAGW-1197 to YL, and NSF grant IBN9003956 to TG andGH. |
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