Institut Jean Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique-AgroParisTech, 78026 Versailles, France.
Plant Cell. 2011 Mar;23(3):1124-37. doi: 10.1105/tpc.110.082792. Epub 2011 Mar 29.
Peroxidases have been shown to be involved in the polymerization of lignin precursors, but it remains unclear whether laccases (EC 1.10.3.2) participate in constitutive lignification. We addressed this issue by studying laccase T-DNA insertion mutants in Arabidopsis thaliana. We identified two genes, LAC4 and LAC17, which are strongly expressed in stems. LAC17 was mainly expressed in the interfascicular fibers, whereas LAC4 was expressed in vascular bundles and interfascicular fibers. We produced two double mutants by crossing the LAC17 (lac17) mutant with two LAC4 mutants (lac4-1 and lac4-2). The single and double mutants grew normally in greenhouse conditions. The single mutants had moderately low lignin levels, whereas the stems of lac4-1 lac17 and lac4-2 lac17 mutants had lignin contents that were 20 and 40% lower than those of the control, respectively. These lower lignin levels resulted in higher saccharification yields. Thioacidolysis revealed that disrupting LAC17 principally affected the deposition of G lignin units in the interfascicular fibers and that complementation of lac17 with LAC17 restored a normal lignin profile. This study provides evidence that both LAC4 and LAC17 contribute to the constitutive lignification of Arabidopsis stems and that LAC17 is involved in the deposition of G lignin units in fibers.
过氧化物酶已被证明参与木质素前体的聚合，但漆酶（EC 1.10.3.2）是否参与组成型木质化仍不清楚。我们通过研究拟南芥中的漆酶 T-DNA 插入突变体来解决这个问题。我们鉴定了两个在茎中强烈表达的基因，LAC4 和 LAC17。LAC17 主要在束间纤维中表达，而 LAC4 在维管束和束间纤维中表达。我们通过将 LAC17（lac17）突变体与两个 LAC4 突变体（lac4-1 和 lac4-2）杂交产生了两个双突变体。单突变体和双突变体在温室条件下正常生长。单突变体的木质素含量略低，而 lac4-1 lac17 和 lac4-2 lac17 突变体的木质素含量分别比对照低 20%和 40%。这些较低的木质素水平导致更高的糖化产率。硫代酸解表明，破坏 LAC17 主要影响束间纤维中 G 木质素单元的沉积，而用 LAC17 互补 lac17 则恢复了正常的木质素图谱。这项研究提供了证据表明，LAC4 和 LAC17 都有助于拟南芥茎的组成型木质化，并且 LAC17 参与纤维中 G 木质素单元的沉积。
