Glycine-rich proteins as structural components of plant cell walls |
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Authors: | C Ringli B Keller U Ryser |
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Institution: | (1) Institute of Plant Biology, University of Zürich, Zollikerstrasse 109, 8008 Zürich (Switzerland), Fax: +41 1 634 8204, e-mail: bkeller@botinst.unizh.ch , CH;(2) Institute of Plant Biology, University of Freiburg, A. Gockelstrasse 3, 1700 Freiburg (Switzerland), CH |
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Abstract: | Glycine-rich proteins (GRPs) have been found in the cell walls of many higher plants and form a third group of structural
protein components of the wall in addition to extensins and proline-rich proteins. The primary sequences of GRPs contain more
than 60% glycine. GRPs are localized mainly in the vascular tissue of the plant, and their coding genes provide an excellent
system to analyze the molecular basis of vascular-specific gene expression. In French bean, the major cell wall GRP has been
localized at the ultrastructural level in the modified primary cell wall of protoxylem. Immunological studies showed that
it forms a major part of these highly extensible and specialized cell walls. Specific digestion of GRP1.8 from bean by collagenase
suggests that it shares structural similarities with collagen. The protein is synthesized by living protoxylem cells as well
as xylem parenchyma cells. After cell death, GRPs are exported from neighboring xylem parenchyma cells to the protoxylem wall,
a rare example of protein transport between cells in plants. We propose that GRPs are part of a repair system of the plant
during the stretching phase of protoxylem. |
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Keywords: | , Cell wall, glycine-rich protein, protoxylem, structural protein, vascular tissue, xylem, |
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