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Dirigent proteins and dirigent sites in lignifying tissuesTissue-specific dirigent protein gene expression and associated dirigent (site) localization were examined in various organs of Forsythia intermedia using tissue printing, in situ mRNA hybridization and immunolabeling techniques, respectively. Dirigent protein gene expression was primarily noted in the undifferentiated cambial regions of stem sections, whereas dirigent protein sites were detected mainly in the vascular cambium and ray parenchyma cell initials. Immunolocalization also revealed cross-reactivity with particular regions of the lignified cell walls, these being coincident with the known sites of initiation of lignin deposition. These latter regions are considered to harbor contiguous arrays of dirigent (monomer binding) sites for initiation of lignin biopolymer assembly. Dirigent protein mRNA expression was also localized in the vascular regions of roots and petioles, whereas in leaves the dirigent sites were primarily associated with the palisade layers and the vascular bundle. That is, dirigent protein mediated lignan biosynthesis was initiated primarily in the cambium and ray cell initial regions of stems as well as in the leaf palisade layers, this being in accordance with the occurrence of the lignans for defense purposes. Within lignified secondary xylem cell walls, however, dirigent sites were primarily localized in the S(1) sublayer and compound middle lamella, these being coincident with previously established sites for initiation of macromolecular lignin biosynthesis. Once initiation occurs, lignification is proposed to continue through template polymerization.
Document ID
20040112391
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Burlat, V.
(Institute of Biological Chemistry, Washington State University Pullman, WA 99164-6340, United States)
Kwon, M.
Davin, L. B.
Lewis, N. G.
Date Acquired
August 21, 2013
Publication Date
July 1, 2001
Publication Information
Publication: Phytochemistry
Volume: 57
Issue: 6
ISSN: 0031-9422
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Plant Biology
Non-NASA Center

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