De Meester Barbara, Van Acker Rebecca, Wouters Marlies, Traversari Silvia, Steenackers Marijke, Neukermans Jenny, Van Breusegem Frank, Déjardin Annabelle, Pilate Gilles, Boerjan Wout
Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, 9052, Ghent, Belgium.
VIB Center for Plant Systems Biology, Technologiepark 71, 9052, Ghent, Belgium.
New Phytol. 2022 Dec;236(6):2075-2090. doi: 10.1111/nph.18366. Epub 2022 Aug 9.
Lignin is one of the main factors causing lignocellulosic biomass recalcitrance to enzymatic hydrolysis. Glasshouse-grown poplars severely downregulated for CINNAMYL ALCOHOL DEHYDROGENASE 1 (CAD1), the enzyme catalysing the last step in the monolignol-specific branch of lignin biosynthesis, have increased saccharification yields and normal growth. Here, we assess the performance of these hpCAD poplars in the field under short rotation coppice culture for two consecutive rotations of 1 yr and 3 yr. While 1-yr-old hpCAD wood had 10% less lignin, 3-yr-old hpCAD wood had wild-type lignin levels. Because of their altered cell wall composition, including elevated levels of cinnamaldehydes, both 1-yr-old and 3-yr-old hpCAD wood showed enhanced saccharification yields upon harsh alkaline pretreatments (up to +85% and +77%, respectively). In contrast with previous field trials with poplars less severely downregulated for CINNAMYL ALCOHOL DEHYDROGENASE (CAD), the hpCAD poplars displayed leaning phenotypes, early bud set, early flowering and yield penalties. Moreover, hpCAD wood had enlarged vessels, decreased wood density and reduced relative and free water contents. Our data show that the phenotypes of CAD-deficient poplars are strongly dependent on the environment and underpin the importance of field trials in translating basic research towards applications.
木质素是导致木质纤维素生物质对酶解具有抗性的主要因素之一。在温室中生长的杨树中，肉桂醇脱氢酶1（CAD1）被严重下调，CAD1是催化木质素生物合成中单木质醇特异性分支最后一步的酶，这些杨树的糖化产量增加且生长正常。在此，我们评估了这些hpCAD杨树在短轮伐期矮林栽培条件下连续两年（1年和3年）的田间表现。1年生的hpCAD木材木质素含量降低了10%，而3年生的hpCAD木材木质素水平与野生型相当。由于其细胞壁组成发生了变化，包括肉桂醛水平升高，1年生和3年生的hpCAD木材在经过苛刻的碱性预处理后糖化产量均有所提高（分别高达+85%和+77%）。与之前对肉桂醇脱氢酶（CAD）下调程度较轻的杨树进行的田间试验不同，hpCAD杨树表现出倾斜的表型、早萌、早花以及产量损失。此外，hpCAD木材的导管增大，木材密度降低，相对含水量和自由含水量减少。我们的数据表明，CAD缺陷型杨树的表型强烈依赖于环境，并突出了田间试验在将基础研究转化为应用方面的重要性。
