The conversion of lignocellulosic feedstocks to fermentable sugar for biofuel production is inefficient, and most strategies to enhance efficiency directly target lignin biosynthesis, with associated negative growth impacts. Here we demonstrate, for both laboratory- and field-grown plants, that expression of Pag-miR408 in poplar (Populus alba × P. glandulosa) significantly enhances saccharification, with no requirement for acid-pretreatment, while promoting plant growth. The overexpression plants show increased accessibility of cell walls to cellulase and scaffoldin cellulose-binding modules. Conversely, Pag-miR408 loss-of-function poplar shows decreased cell wall accessibility. Overexpression of Pag-miR408 targets three Pag-LACCASES, delays lignification, and modestly reduces lignin content, S/G ratio and degree of lignin polymerization. Meanwhile, the LACCASE loss of function mutants exhibit significantly increased growth and cell wall accessibility in xylem. Our study shows how Pag-miR408 regulates lignification and secondary growth, and suggest an effective approach towards enhancing biomass yield and saccharification efficiency in a major bioenergy crop.

将木质纤维素原料转化为用于生物燃料生产的可发酵糖的效率低下，大多数提高效率的策略直接针对木质素生物合成，从而产生相关的负面增长影响。在这里，我们证明，对于实验室和田间种植的植物，Pag-miR408在杨树（白杨× P. 腺）中的表达显着增强糖化，无需酸预处理，同时促进植物生长。过表达植物显示出细胞壁对纤维素酶和纤维素结合模块中的支架的可及性增加。相反，Pag-miR408功能丧失的杨树显示细胞壁可及性降低。Pag-miR408的过表达靶向三个Pag-LACCASES，延迟木质化，并适度降低木质素含量、S/G 比和木质素聚合度。同时，LACCASE功能缺失突变体表现出木质部生长和细胞壁可及性显着增加。我们的研究展示了Pag-miR408如何调节木质化和次生生长，并提出了一种提高主要生物能源作物的生物量产量和糖化效率的有效方法。