PLANT PHYSIOLOGY , Vol 110, Issue 3 825-834, Copyright © 1996 by American Society of Plant Biologists
|
BIOCHEMISTRY AND ENZYMOLOGY |
Characterization of a New Lectin of Soybean Vegetative Tissues
S. R. Spilatro, G. R. Cochran, R. E. Walker, K. L. Cablish and C. C. Bittner
Department of Biology, Marietta College, Marietta, Ohio 45750-4016
Lectins are carbohydrate-binding proteins that occur widely among plants.
Lectins of plant vegetative tissues are less well characterized than those
of seeds. Previously, a protein of soybean (Glycine max [L.] Merr.) leaves
was shown to possess properties similar to the seed lectin. Here we show
that the N-terminal amino acid sequence of this protein shares 63% identity
with the seed lectin. Immunoblot analysis indicated that the protein occurs
in leaves, petioles, stems, and cotyledons of seedlings but not in seeds.
These observations prompted designation of the protein as a soybean
vegetative lectin (SVL). Immunohistochemical localization in leaves
indicated that SVL was localized to the vacuoles of bundle-sheath and
paraveinal mesophyll cells. Removal of sink tissues or exposure to
atmospheric methyl jasmonate caused increased levels of SVL in leaves and
cotyledons. Co-precipitation of SVL and the soybean vegetative storage
protein (VSP) during purification suggested an interaction between these
proteins. SVL-horseradish peroxidase conjugate bound to dot blots of VSP or
SVL, and binding was inhibited by porcine stomach mucin and heparin but not
simple carbohydrates. Binding between SVL and VSP and similarities in
localization and regulation support a possible in vivo interaction between
these proteins.
