DUBBS, WESLEY EMANUEL* AND HOWARD GRIMES. Department of Biology, Portland State University, P.O. Box 751, Portland, OR 97207. - Characterization of a specialized cell layer in the soybean pod wall and its potential role in wound response
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Specialized anatomical and biochemical features mark the presence of a
previously uncharacterized cell layer in the pod wall of soybean
(Glycine max L.). The cells of this layer, termed the
mid-pericarp layer (MPL), are larger than other
cells of the mesocarp and are highly branched. The entire MPL appears
to form an elaborate interdigitated network running in a single plane
parallel with the pod surface just outside vascular bundles between
the dorsal and ventral sutures. A striking feature of the cell walls
between individual MPL cells are regions of abrupt cell wall thinning,
~30 nm. These thin cell walls are occasionally found disrupted.
Following mechanical wounding of the pod wall 40 kD F-dextran moves
extensively into the MPL. In addition, cutting through the pod wall
causes exudate flow from the MPL. Isoforms of lipoxygenase
constitutes over 38% of the total soluble protein in this exudate and
these extracts contain active lipxoygenases as assayed by
O2 consumption using linolenic and linoleic acids as
substrates. The exudate is relatively high in the vegetative
lipoxygenase isoforms, VLXA, -B and -C which
specifically co-localize to the cytoplasm in cells of the MPL. The
MPL may function during mechanical wounding by generating
lipoxygenase-derived compounds as a general defense mechanism found in
leguminous plants.
Key words: Glycine max,lipoyxgenase,mesocarp,pod,soybean,wounding