Catechyl lignin (C-lignin) is a linear homopolymer of caffeyl alcohol found in the seed coats of diverse plant species. Its properties make it a natural source of carbon fibers and high-value chemicals, but the mechanism of in planta polymerization of caffeyl alcohol remains unclear. In the ornamental plant Cleome hassleriana, lignin biosynthesis in the seed coat switches from guaiacyl lignin to C-lignin at ~12 d after pollination. Here we found that the transcript profile of the laccase gene ChLAC8 parallels the accumulation of C-lignin during seed coat development. Recombinant ChLAC8 oxidizes caffeyl and sinapyl alcohols, generating their corresponding dimers or trimers in vitro, but cannot oxidize coniferyl alcohol. We propose a basis for this substrate preference based on molecular modeling/docking experiments. Suppression of ChLAC8 expression led to significantly reduced C-lignin content in the seed coats of transgenic Cleome plants. Feeding of ¹³C-caffeyl alcohol to the Arabidopsis (Arabidopsis thaliana) caffeic acid o-methyltransferase mutant resulted in no incorporation of ¹³C into C-lignin, but expressing ChLAC8 in this genetic background led to appearance of C-lignin with >40% label incorporation. These results indicate that ChLAC8 is required for C-lignin polymerization and determines lignin composition when caffeyl alcohol is available.

儿茶素木质素（C-木质素）是咖啡醇的线性均聚物，存在于多种植物种的种皮中。它的特性使其成为碳纤维和高价值化学品的天然来源，但是咖啡醇在植物体内的聚合机理仍不清楚。在观赏植物油茶（Cleome hassleriana）中，授粉后约12天，种皮中木质素的生物合成从愈创木（G）木质素转换为C-木质素。在这里，我们发现漆酶基因ChLAC8的转录本谱与种皮发育过程中C-木质素的积累平行。重组ChLAC8可氧化咖啡醇和芥子醇，在体外产生其相应的二聚体或三聚体，但不能氧化松柏醇。我们基于分子建模/对接实验为这种底物偏爱提出了基础。ChLAC8表达的抑制导致转基因Cleome植物种皮中C-木质素含量显着降低。向拟南芥咖啡酸O-甲基转移酶（comt）突变体中饲喂13C-咖啡醇不会导致将13C掺入C-木质素中，但在这种遗传背景下表达ChLAC8会导致C-木质素的出现，其中标签掺入量超过40％ 。这些结果表明，ChLAC8是C-木质素聚合所必需的，并在可获得咖啡醇的情况下确定木质素的组成。但是在这种遗传背景下表达ChLAC8会导致C-木质素的出现，其中标签掺入率超过40％。这些结果表明，ChLAC8是C-木质素聚合所必需的，并在可获得咖啡醇的情况下确定木质素的组成。但是在这种遗传背景中表达ChLAC8会导致C-木质素的出现，其中标签掺入率超过40％。这些结果表明，ChLAC8是C-木质素聚合所必需的，并在可获得咖啡醇的情况下确定木质素的组成。