At present, a cooperative process hypothesis is used to explain the supply of enzyme (class III peroxidases and/or laccases) and substrates during lignin polymerization. However, it remains elusive how xylem cells meet the needs of early lignin rapid polymerization during secondary cell wall formation. Here we provide evidence that a mitochondrial ascorbate peroxidase (PtomtAPX) is responsible for autonomous lignification during the earliest stage of secondary cell wall formation in Populus tomentosa. PtomtAPX was relocated to cell walls undergoing programmed cell death and catalysed lignin polymerization in vitro. Aberrant phenotypes were caused by altered PtomtAPX expression levels in P. tomentosa. These results reveal that PtomtAPX is crucial for catalysing lignin polymerization during the early stages of secondary cell wall formation and xylem development, and describe how xylem cells provide autonomous enzymes needed for lignin polymerization during rapid formation of the secondary cell wall by coupling with the programmed cell death process.

目前，协同过程假设用于解释木质素聚合过程中酶（III类过氧化物酶和/或漆酶）和底物的供应。然而，在次生细胞壁形成过程中，木质部细胞如何满足早期木质素快速聚合的需求仍然难以捉摸。在这里，我们提供的证据表明，线粒体抗坏血酸过氧化物酶 (PtomtAPX) 负责毛白杨次生细胞壁形成的最早阶段的自主木质化。PtomtAPX 被重新定位到细胞壁，在体外经历程序性细胞死亡和催化的木质素聚合。异常表型是由P. tomentosa中 PtomtAPX 表达水平改变引起的. 这些结果表明，PtomtAPX 在次生细胞壁形成和木质部发育的早期阶段对于催化木质素聚合至关重要，并描述了木质部细胞如何通过与程序化细胞偶联在次生细胞壁快速形成过程中提供木质素聚合所需的自主酶死亡过程。