PLANT PHYSIOLOGY , Vol 103, Issue 4 1061-1066, Copyright © 1993 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Soybean Seed Coat Peroxidase (A Comparison of High-Activity and Low-Activity Genotypes)
M. Gijzen, R. van Huystee and R. I. Buzzell
Agriculture Canada, London Research Centre, 1391 Sandford Street, London, Ontario, Canada N5V 4T3 (M.G.)
Peroxidase activity in the seed coats of soybean (Glycine max [L.] Merr.)
is controlled by the Ep locus. We compared peroxidase activity in cell-free
extracts from seed coat, root, and leaf tissues of three EpEp cultivars
(Harosoy 63, Harovinton, and Coles) to three epep cultivars (Steele,
Marathon, and Raiden). Extracts from the seed coats of EpEp cultivars were
100-fold higher in specific activity than those from epep cultivars, but
there was no difference in specific activity in crude root or leaf
extracts. Isoelectric focusing of root tissue extracts and staining for
peroxidase activity showed that EpEp cultivars had a root peroxidase of
identical isoelectric point to the seed coat peroxidase, whereas roots of
the epep types were lacking that peroxidase, indicating that the Ep locus
may also affect expression in the root. In seed coat extracts, peroxidase
was the most abundant soluble protein in EpEp cultivars, whereas this
enzyme was present only in trace amounts in epep genotypes, as determined
by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Histochemical
localization of peroxidase activity in seed coats of EpEp cultivars shows
that the enzyme occurs predominately in the cytoplasm of hourglass cells of
the subepidermis. No obvious difference in the gross or microscopic
structure of the seed coat was observed to be associated with the Ep locus.
These results suggest that soybean seed coat peroxidase may be involved in
processes other than seed coat biosynthesis.
