TITLE:
Common Mechanism of Lignification of Compression Wood in Conifers and Buxus
AUTHORS:
Hideto Hiraide, Masato Yoshida, Saori Sato, Hiroyuki Yamamoto
KEYWORDS:
Lignification, Laccase, Buxus, Reaction Wood, Compression Wood
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.7 No.7,
May
25,
2016
ABSTRACT: Woody plants develop a
specialized secondary xylem known as reaction wood to
enable formation of an ideal shape. Reaction wood in coniferous species is
known as compression wood, and that of woody angiosperms as tension wood.
However, the genus Buxus which is
classified as an angiosperm, forms compression-wood-like reaction wood. We
investigated the mechanism of lignification in coniferous compression wood and Buxus reaction wood: 1) Several lignin
synthesis genes were upregulated in
differentiating reaction wood of Buxus
microphylla; 2) B. microphylla possesses a specific laccase gene that is expressed specifically in
differentiating reaction wood (BmLac4);
3) laccase activity localization was closely related to lignification of
reaction wood, and laccase activity was high in the secondary wall middle
layer; 4) in reaction wood cell walls, galactan was present in the outer
portion of the secondary wall middle layer, and the level of xylan was reduced.
These findings suggest that lignification in B. microphylla reaction wood is identical to that of coniferous
compression wood. These may represent general mechanisms of increasing lignin
content in various reaction woods.