Involvement of AtLAC15 in lignin synthesis in seeds and in root elongation of Arabidopsis
Involvement of AtLAC15 in lignin synthesis in seeds and in root elongation of Arabidopsis
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DOI：
10.1007/s00425-006-0300-6
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发表时间：
2006-10-01
期刊：
影响因子：
4.3
通讯作者：
Wu, Yajun
中科院分区：
文献类型：
--
作者：
Liang, Mingxiang;Davis, Elizabeth;Wu, Yajun
漆酶（EC 1.10.3.2或p-联苯酚：二氧氧化还原酶）基于其体外酶活性和与植物中的木质化过程的密切相关性而被提出参与植物中的木质素合成。尽管多年的研究，漆酶在木质素合成中的作用的遗传证据仍然缺失。通过筛选拟南芥漆酶基因家族的突变体，我们鉴定了两个漆酶基因AtLAC 15（At 5g 48100）的突变体，其种皮为淡棕色或黄色，类似于透明种皮（tt）的突变体表型。化学成分分析表明，突变体种子有近30%的可提取木质素含量减少和59%的可溶性原花青素或缩合单宁增加相比，野生型种子。在体外酶测定中，在不存在H2 O2的情况下，发育中的突变体种子显示松柏醇的聚合活性显著降低。在使用发育中的野生型种子的体外测定中形成的二聚体中，23%的键是β-O-4，其类似于天然木质素中形成的主要键。证据强烈支持AtLAC 15参与植物中的木质素合成。据我们所知，这是漆酶在木质素合成中的作用的第一个遗传证据。在突变体中还观察到种皮透性、种子萌发和根伸长的变化。
Laccase, EC 1.10.3.2 or p-diphenol:dioxygen oxidoreductase, has been proposed to be involved in lignin synthesis in plants based on its in vitro enzymatic activity and a close correlation with the lignification process in plants. Despite many years of research, genetic evidence for the role of laccase in lignin synthesis is still missing. By screening mutants available for the annotated laccase gene family in Arabidopsis, we identified two mutants for a single laccase gene, AtLAC15 (At5g48100) with a pale brown or yellow seed coat which resembled the transparent testa (tt) mutant phenotype. A chemical component analysis revealed that the mutant seeds had nearly a 30% decrease in extractable lignin content and a 59% increase in soluble proanthocyanidin or condensed tannin compared with wild-type seeds. In an in vitro enzyme assay, the developing mutant seeds showed a significant reduction in polymerization activity of coniferyl alcohol in the absence of H2O2. Among the dimers formed in the in vitro assay using developing wild-type seeds, 23% of the linkages were beta-O-4 which resembles the major linkages formed in native lignin. The evidence strongly supports that AtLAC15 is involved in lignin synthesis in plants. To our knowledge, this is the first genetic evidence for the role of laccase in lignin synthesis. Changes in seed coat permeability, seed germination and root elongation were also observed in the mutant.