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.

中文翻译：

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杨树的田间和糖化性能在 CAD1 中严重下调。

木质素是导致木质纤维素生物质抗酶解的主要因素之一。温室种植的杨树肉桂醇脱氢酶 1 (CAD1) 严重下调，该酶催化木质素生物合成的单一木质醇特定分支的最后一步，增加了糖化产量和正常生长。在这里，我们评估了这些 hpCAD 杨树在短期轮作矮林栽培下连续两次轮作 1 年和 3 年的表现。使用 1 年的 hpCAD 木材木质素含量减少 10%，而使用 3 年的 hpCAD 木材则具有野生型木质素水平。由于细胞壁组成发生改变，包括肉桂醛含量升高，1 年树龄和 3 年树龄的 hpCAD 木材在苛刻的碱性预处理后均表现出更高的糖化率（分别高达 +85% 和 +77%）。与之前对肉桂醇脱氢酶 (CAD) 不太严重下调的杨树进行的田间试验相比，hpCAD 杨树表现出倾斜表型、早芽、早开花和产量损失。此外，hpCAD 木材的血管增大，木材密度降低，相对水和游离水含量降低。我们的数据表明，CAD 缺陷杨树的表型强烈依赖于环境，并支持田间试验在将基础研究转化为应用方面的重要性。