Lu Da, Yuan Xianghe, Kim Sung-Jin, Marques Joaquim V, Chakravarthy P Pawan, Moinuddin Syed G A, Luchterhand Randi, Herman Barri, Davin Laurence B, Lewis Norman G
Institute of Biological Chemistry, Washington State University, Pullman, WA, USA.
Puyallup Research and Extension Center, Washington State University, Puyallup, WA, USA.
Plant Biotechnol J. 2017 Aug;15(8):970-981. doi: 10.1111/pbi.12692. Epub 2017 Mar 7.
A foundational study assessed effects of biochemical pathway introduction into poplar to produce eugenol, chavicol, p-anol, isoeugenol and their sequestered storage products, from potentially available substrates, coniferyl and p-coumaryl alcohols. At the onset, it was unknown whether significant carbon flux to monolignols vs. other phenylpropanoid (acetate) pathway metabolites would be kinetically favoured. Various transgenic poplar lines generated eugenol and chavicol glucosides in ca. 0.45% (~0.35 and ~0.1%, respectively) of dry weight foliage tissue in field trials, as well as their corresponding aglycones in trace amounts. There were only traces of any of these metabolites in branch tissues, even after ~4-year field trials. Levels of bioproduct accumulation in foliage plateaued, even at the lowest introduced gene expression levels, suggesting limited monolignol substrate availability. Nevertheless, this level still allows foliage collection for platform chemical production, with the remaining (stem) biomass available for wood, pulp/paper and bioenergy product purposes. Several transformed lines displayed unexpected precocious flowering after 4-year field trial growth. This necessitated terminating (felling) these particular plants, as USDA APHIS prohibits the possibility of their interacting (cross-pollination, etc.) with wild-type (native plant) lines. In future, additional biotechnological approaches can be employed (e.g. gene editing) to produce sterile plant lines, to avoid such complications. While increased gene expression did not increase target bioproduct accumulation, the exciting possibility now exists of significantly increasing their amounts (e.g. 10- to 40-fold plus) in foliage and stems via systematic deployment of numerous 'omics', systems biology, synthetic biology and metabolic flux modelling approaches.
一项基础研究评估了将生化途径引入杨树以从潜在可用底物松柏醇和对香豆醇生产丁香酚、异丁子香酚、对丙烯基苯酚、异丁香酚及其隔离储存产物的效果。一开始，尚不清楚向单木质醇与其他苯丙烷（乙酸）途径代谢物的显著碳通量在动力学上是否更有利。在田间试验中，各种转基因杨树品系在约0.45%（分别约为0.35%和0.1%）的干重叶片组织中产生了丁香酚和异丁子香酚糖苷，以及痕量的相应苷元。即使经过约4年的田间试验，这些代谢物在树枝组织中也只有痕量。即使在引入的基因表达水平最低时，叶片中生物产品的积累水平也趋于平稳，这表明单木质醇底物的可用性有限。然而，这个水平仍然允许收集叶片用于平台化学品生产，剩余的（茎）生物质可用于木材、纸浆/纸张和生物能源产品用途。经过4年的田间试验生长后，几个转化品系出现了意外的早熟开花现象。由于美国农业部动植物卫生检验局禁止这些特定植物与野生型（本地植物）品系相互作用（异花授粉等）的可能性，因此有必要将这些特定植物砍伐。未来，可以采用其他生物技术方法（如基因编辑）来培育不育植物品系，以避免此类复杂情况。虽然增加基因表达并没有增加目标生物产品的积累，但现在令人兴奋的可能性是，通过系统地部署众多“组学”、系统生物学、合成生物学和代谢通量建模方法，显著增加它们在叶片和茎中的含量（例如增加10至40倍以上）。
