背景回顾：Plant lignification exhibits notable plasticity. Lignin in many species, including Populus spp., has long been known to be decorated with p-hydroxybenzoates. 

提出问题：However, the molecular basis for such structural modification remains undetermined.

主要发现：Here, we report the identification and characterization of a Populus BAHD family acyltransferase that catalyses monolignol p-hydroxybenzoylation, thus controlling the formation of p-hydroxybenzoylated lignin structures. 

结果1-PHBMT1酶活：We reveal that Populus acyltransferase PHBMT1 kinetically preferentially usesp-hydroxybenzoyl-CoA to acylate syringyl lignin monomer sinapyl alcohol in vitro. 

结果2-PHBMT1敲除和过表达表型：Consistently, disrupting PHBMT1 in Populus via CRISPR–Cas9 gene editing nearly completely depletes p-hydroxybenzoates of stem lignin; conversely, overexpression of PHBMT1 enhances stem lignin p-hydroxybenzoylation, suggesting PHBMT1 functions as a prime monolignol p-hydroxybenzoyltransferase in planta. 

结果3-对羟基苯甲酸酯修饰对木质素结构的影响：Altering lignin p-hydroxybenzoylation substantially changes the lignin solvent dissolution rate, indicative of its structural significance on lignin physiochemical properties. 

结论：Identification of monolignol p-hydroxybenzoyltransferase offers a valuable tool for tailoring lignin structure and physiochemical properties and for engineering the industrially important platform chemical in woody biomass.

 摘 要 

植物的木质化具有很强的可塑性。一直以来，人们就知道包括杨树在内的很多物种中的木质素会发生对羟基苯甲酸酯修饰。但是，这种结构修饰的分子基础还不清楚。本文中，作者在杨树中鉴定到了一个催化木质素单体对羟基苯甲酰化的BAHD家族酰基转移酶，该酶控制了对羟基苯甲酸酯修饰木质素结构的形成。作者发现杨树的酰基转移酶PHBMT1在体外的酶动力学实验中，会优先使用对羟基苯甲酰辅酶A来酰化丁香基木质素单体芥子醇。与此一致，通过CRISPR–Cas9基因编辑技术扰乱杨树中PHBMT1基因的表达，会几乎消除茎木质素中的所有对羟基苯甲酸酯；相反，过表达PHBMT1基因增加了茎木质素中的对羟基苯甲酸酯，说明PHBMT1在植物中作为木质素单体对羟基苯甲酰转移酶发挥作用。改变木质素的对羟基苯甲酰化会极大地改变木质素的溶剂溶解率，说明了对羟基苯甲酸酯修饰对于木质素理化性质的重要性。木质素单体对羟基苯甲酰转移酶的鉴定为定制木质素结构和理化性质，以及为工业上木材生物量重要化合物的改良提供了一个重要的工具。