Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing 100083, China; College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China.
School of Management, Qingdao Agricultural University, Shandong 266109, China.
Int J Biol Macromol. 2021 Oct 1;188:983-992. doi: 10.1016/j.ijbiomac.2021.08.077. Epub 2021 Aug 14.
Plant laccases have been proposed to participate in lignin biosynthesis. However, there is no direct evidence that individual laccases in Populus can polymerize lignin monomers and alter cell wall structure. Here, a Populus laccase, PtrLAC16, was expressed and purified in a eukaryotic system. Enzymatic analysis of PtrLAC16 showed that it could polymerize lignin monomers in vitro. PtrLAC16 preferred sinapyl alcohol, and this preference is associated with an altered S/G ratio in transgenic Populus lines. PtrLAC16 was localized exclusively in the cell walls of stem vascular tissue, and a reduction in PtrLAC16 expression led to a significant decrease in lignin content and altered cell wall structure. There was a direct correlation between the inhibition of PtrLAC16 expression and structural changes in the stem cell wall of Populus. This study provides direct evidence that PtrLAC16 plays a key role in the polymerization of lignin monomers, especially for sinapyl lignin, and affects the formation of xylem cell walls in Populus.
植物漆酶被认为参与木质素的生物合成。然而，目前尚无直接证据表明杨树中的个别漆酶能够聚合木质素单体并改变细胞壁结构。本研究中，在真核系统中表达和纯化了杨树漆酶 PtrLAC16。PtrLAC16 的酶学分析表明，它可以在体外聚合木质素单体。PtrLAC16 优先选择芥子醇，这种偏好与转基因杨树中 S/G 比的改变有关。PtrLAC16 仅定位于茎维管束组织的细胞壁中，降低 PtrLAC16 的表达水平会导致木质素含量显著降低和细胞壁结构的改变。PtrLAC16 的表达抑制与杨树茎细胞壁的结构变化之间存在直接的相关性。本研究提供了直接证据，表明 PtrLAC16 在木质素单体，特别是芥子醇木质素的聚合中起关键作用，并影响杨树木质部细胞壁的形成。
