Cell walls in crops and trees have been engineered for production of biofuels and commodity chemicals, but engineered varieties often fail multi-year field trials and are not commercialized. We engineered reduced expression of a pectin biosynthesis gene (Galacturonosyltransferase 4, GAUT4) in switchgrass and poplar, and find that this improves biomass yields and sugar release from biomass processing. Both traits were maintained in a 3-year field trial of GAUT4-knockdown switchgrass, with up to sevenfold increased saccharification and ethanol production and sixfold increased biomass yield compared with control plants. We show that GAUT4 is an α-1,4-galacturonosyltransferase that synthesizes homogalacturonan (HG). Downregulation of GAUT4 reduces HG and rhamnogalacturonan II (RGII), reduces wall calcium and boron, and increases extractability of cell wall sugars. Decreased recalcitrance in biomass processing and increased growth are likely due to reduced HG and RGII cross-linking in the cell wall.

中文翻译：

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果胶生物合成的下调改善了糖的释放和生物燃料作物的生长。

作物和树木的细胞壁已经过工程化，用于生产生物燃料和日用化学品，但工程化品种通常无法通过多年的田间试验，因此无法商业化。我们设计了柳枝and和杨树中果胶生物合成基因（半乳糖醛糖基转移酶4，GAUT4）的表达降低，并发现这可以提高生物量产量和生物量加工过程中的糖释放。在为期3年的GAUT4敲除柳枝switch田间试验中，这两个性状均得到保留，与对照植物相比，糖化和乙醇产量提高了多达7倍，生物量产量提高了6倍。我们显示，GAUT4是合成高半乳糖醛酸（HG）的α-1,4-半乳糖醛糖基转移酶。GAUT4的下调降低了HG和鼠李半乳糖醛酸聚糖II（RGII），降低了壁中的钙和硼，并增加了细胞壁糖的提取能力。生物量加工过程中顽固抵抗力的降低和生长的增加可能是由于细胞壁中HG和RGII交联减少所致。