Shen Mengxiao, Liu Yadi, Xu Yaoming, Sun Yu, Sun Leiqian, Feng Yuping, Chen Mengyuan, Zhang Chong, Li Hui, Lu Hai
State Key Laboratory of Tree Genetics and Breeding, The Tree and Ornamental Plant Breeding and Biotechnology Laboratory of National Forestry and Grassland Administration, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China.
State Key Laboratory of Tree Genetics and Breeding, The Tree and Ornamental Plant Breeding and Biotechnology Laboratory of National Forestry and Grassland Administration, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China.
Int J Biol Macromol. 2025 Sep;321(Pt 4):146547. doi: 10.1016/j.ijbiomac.2025.146547. Epub 2025 Aug 7.
Plant laccase is a crucial enzyme that plays a role in the polymerization of lignin macromolecules. Previous research on laccases has primarily concentrated on the synthesis of lignin in the secondary walls of xylem. In this study, PtrLAC17 was localized in both the secondary cell walls of the xylem in the stem and the guard cell walls of Populus trichocarpa Torr, functioning as a key enzyme for lignin polymerization. Enzymatic analysis revealed that PtrLAC17-encoded enzyme can polymerizes lignin monomers in vitro, with a preference for sinapyl alcohol. In Populus overexpressing PtrLAC17 (OE-PtrLAC17s), lignin content significantly increased in both the guard cell ventral wall and the xylem cell wall, while it decreased in antisense lines (AS-PtrLAC17s) and mutants lines. The syringyl/guaiacyl (S/G) lignin ratio was also varied in the transgenic Populus lines. OE-PtrLAC17s exhibited reduced stomatal apertures, conferring enhanced drought resistance, whereas AS-PtrLAC17 and mutants showed increased stomatal apertures, resulting in decreased drought tolerance. These results demonstrate that elevated lignin deposition in of guard cells walls reduces stomatal aperture and enhances plant drought resistance. Additionally, lignin deposition in stem secondary cell wall increases the thickness of the fiber cell wall and improves hydraulic conductivity. These findings provide new insights into how plant laccase in Populus synergistically regulates drought stress response by catalyzing lignin polymerization in both the secondary cell wall of the xylem in the stem and stomatal cell wall.
植物漆酶是一种在木质素大分子聚合过程中起作用的关键酶。先前对漆酶的研究主要集中在木质部次生壁中木质素的合成。在本研究中，PtrLAC17定位于毛果杨茎木质部的次生细胞壁和保卫细胞壁中，作为木质素聚合的关键酶发挥作用。酶活性分析表明，PtrLAC17编码的酶能够在体外聚合木质素单体，对芥子醇具有偏好性。在过表达PtrLAC17的杨树（OE-PtrLAC17s）中，保卫细胞腹侧细胞壁和木质部细胞壁中的木质素含量均显著增加，而在反义株系（AS-PtrLAC17s）和突变株系中则降低。转基因杨树株系中紫丁香基/愈创木基（S/G）木质素比率也有所不同。OE-PtrLAC17s表现出气孔孔径减小，从而增强了抗旱性，而AS-PtrLAC17和突变体则表现出气孔孔径增大，导致耐旱性降低。这些结果表明，保卫细胞壁中木质素沉积的增加会减小气孔孔径并增强植物的抗旱性。此外，茎次生细胞壁中的木质素沉积增加了纤维细胞壁的厚度并提高了水力传导率。这些发现为杨树中的植物漆酶如何通过催化茎木质部次生细胞壁和气孔细胞壁中的木质素聚合来协同调节干旱胁迫响应提供了新的见解。
