PLANT PHYSIOLOGY , Vol 104, Issue 3 917-923, Copyright © 1994 by American Society of Plant Biologists
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PLANT-MICROBE INTERACTIONS |
Cyclic [beta]-1,6-1,3-Glucans of Bradyrhizobium japonicum USDA 110 Elicit Isoflavonoid Production in the Soybean (Glycine max) Host
K. J. Miller, J. A. Hadley and D. L. Gustine
Graduate Programs in Genetics (K.J.M.) and Plant Physiology (K.J.M., D.L.G.), Departments of Food Science (K.J.M., J.A.H.) and Agronomy (D.L.G.), The Pennsylvania State University, University Park, Pennsylvania 16802
High levels of cyclic [beta]-1,6-1,3-glucans (e.g. 0.1 mg mg-1 of total
protein) are synthesized by free-living cells as well as by bacteroids of
Bradyrhizobium japonicum USDA 110 (K.J. Miller, R.S. Gore, R. Johnson, A.J.
Benesi, V.N. Reinhold [1990] J Bacteriol 172: 136-142; R.S. Gore and K.J.
Miller [1993] Plant Physiol 102: 191-194). These molecules share structural
features with glucan fragments isolated from the mycelial cell wall of the
soybean (Glycine max) pathogen Phytophthora megasperma. These latter
glucans have been shown to be potent elicitors (at nanogram levels) of the
phytoalexin glyceollin in G. max. Using the well-characterized soybean
cotyledon bioassay, we now show that the cyclic [beta]-1,6-1,3-glucans of
B. japonicum USDA 110 are also biologically active elicitors of glyceollin
production (but at microgram levels). We further show that both classes of
[beta]-glucans elicit the production of the isoflavone daidzein within
soybean cotyledon wound droplets.
