Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Umeå, Sweden.
Enhet Produktionssystem och Material, RISE Research Institutes of Sweden, Växjö, Sweden.
Plant Biotechnol J. 2023 May;21(5):1005-1021. doi: 10.1111/pbi.14012. Epub 2023 Feb 3.
Trees constitute promising renewable feedstocks for biorefinery using biochemical conversion, but their recalcitrance restricts their attractiveness for the industry. To obtain trees with reduced recalcitrance, large-scale genetic engineering experiments were performed in hybrid aspen blindly targeting genes expressed during wood formation and 32 lines representing seven constructs were selected for characterization in the field. Here we report phenotypes of five-year old trees considering 49 traits related to growth and wood properties. The best performing construct considering growth and glucose yield in saccharification with acid pretreatment had suppressed expression of the gene encoding an uncharacterized 2-oxoglutarate-dependent dioxygenase (2OGD). It showed minor changes in wood chemistry but increased nanoporosity and glucose conversion. Suppressed levels of SUCROSE SYNTHASE, (SuSy), CINNAMATE 4-HYDROXYLASE (C4H) and increased levels of GTPase activating protein for ADP-ribosylation factor ZAC led to significant growth reductions and anatomical abnormalities. However, C4H and SuSy constructs greatly improved glucose yields in saccharification without and with pretreatment, respectively. Traits associated with high glucose yields were different for saccharification with and without pretreatment. While carbohydrates, phenolics and tension wood contents positively impacted the yields without pretreatment and growth, lignin content and S/G ratio were negative factors, the yields with pretreatment positively correlated with S lignin and negatively with carbohydrate contents. The genotypes with high glucose yields had increased nanoporosity and mGlcA/Xyl ratio, and some had shorter polymers extractable with subcritical water compared to wild-type. The pilot-scale industrial-like pretreatment of best-performing 2OGD construct confirmed its superior sugar yields, supporting our strategy.
树木是生物炼制中具有前景的可再生原料，可以通过生化转化进行利用，但由于其木质部的抗性，限制了其对工业的吸引力。为了获得木质部抗性降低的树木，曾进行了大规模的基因工程实验，盲目靶向木质部形成过程中表达的基因，选择了代表 7 种构建体的 32 个系进行田间特征分析。在这里，我们报告了 5 年生树木的表型，考虑了 49 个与生长和木材特性相关的性状。在酸预处理的糖化实验中，考虑到生长和葡萄糖产率，表现最好的构建体是 2- 酮戊二酸依赖性双加氧酶（2OGD）编码基因表达受抑制的构建体。它的木材化学性质变化较小，但纳米孔隙率和葡萄糖转化率增加。蔗糖合酶（SuSy）和肉桂酸 4-羟化酶（C4H）的表达水平降低，以及 ADP-核糖基化因子 ZAC 的 GTP 酶激活蛋白的表达水平增加，导致生长显著减少和解剖结构异常。然而，C4H 和 SuSy 构建体分别显著提高了糖化实验中未经预处理和预处理条件下的葡萄糖产率。未经预处理和预处理的糖化实验中，与高葡萄糖产率相关的性状不同。未经预处理时，碳水化合物、酚类和张木含量与产率和生长呈正相关，木质素含量和 S/G 比为负相关，预处理后产率与 S 木质素呈正相关，与碳水化合物含量呈负相关。具有高葡萄糖产率的基因型具有更高的纳米孔隙率和 mGlcA/Xyl 比，并且一些在亚临界水中可提取的聚合物的长度较短，与野生型相比。表现最好的 2OGD 构建体的中试规模工业类似预处理证实了其优异的糖产率，支持了我们的策略。
