PLANT PHYSIOLOGY , Vol 114, Issue 1 363-372, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Al-Induced, 51-Kilodalton, Membrane-Bound Proteins Are Associated with Resistance to Al in a Segregating Population of Wheat
G. J. Taylor, A. Basu, U. Basu, J. J. Slaski, G. Zhang and A. Good
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
Incorporation of 35S into protein is reduced by exposure to Al in wheat
(Triticum aestivum), but the effects are genotype-specific. Exposure to 10
to 75 [mu]M Al had little effect on 35S incorporation into total protein,
nuclear and mitochondrial protein, microsomal protein, and cytosolic
protein in the Al-resistant cultivar PT741. In contrast, 10 [mu]M Al
reduced incorporation by 21 to 38% in the Al-sensitive cultivar Katepwa,
with effects becoming more pronounced (31-62%) as concentrations of Al
increased. We previously reported that a pair of 51-kD membrane-bound
proteins accumulated in root tips of PT741 under conditions of Al stress.
We now report that the 51-kD band is labeled with 35S after 24 h of
exposure to 75 [mu]M Al. The specific induction of the 51-kD band in PT741
suggested a potential role of one or both of these proteins in mediating
resistance to Al. Therefore, we analyzed their expression in single plants
from an F2 population arising from a cross between the PT741 and Katepwa
cultivars. Accumulation of 1,3-[beta]-glucans (callose) in root tips after
24 h of exposure to 100 [mu]M Al indicated that this population segregated
for Al resistance in about a 3:1 ratio. A close correlation between
resistance to Al (low callose content of root tips) and accumulation of the
51-kD band was observed, indicating that at least one of these proteins
cosegregates with the Al-resistance phenotype. As a first step in
identifying a possible function, we have demonstrated that the 51-kD band
is most clearly associated with the tonoplast. Whereas Al has been reported
to stimulate the activity of the tonoplast H+-ATPase and H+-PPase,
antibodies raised against these proteins did not cross-react with the 51-kD
band. Efforts are now under way to purify this protein from
tonoplast-enriched fractions.
