Department of Wood Science, University of British Columbia, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.
Department of Energy, Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin-Madison, 1552 University Avenue, Madison, WI, 53726, USA.
New Phytol. 2022 Jul;235(1):234-246. doi: 10.1111/nph.18136. Epub 2022 May 4.
Renewed interests in the development of bioenergy, biochemicals, and biomaterials have elicited new strategies for engineering the lignin of biomass feedstock plants. This study shows, for the first time, that 3,4-dihydroxybenzoate (DHB) is compatible with the radical coupling reactions that assemble polymeric lignin in plants. We introduced a bacterial 3-dehydroshikimate dehydratase into hybrid poplar (Populus alba × grandidentata) to divert carbon flux away from the shikimate pathway, which lies upstream of lignin biosynthesis. Transgenic poplar wood had up to 33% less lignin with p-hydroxyphenyl units comprising as much as 10% of the lignin. Mild alkaline hydrolysis of transgenic wood released fewer ester-linked p-hydroxybenzoate groups than control trees, and revealed the novel incorporation of cell-wall-bound DHB, as well as glycosides of 3,4-dihydroxybenzoic acid (DHBA). Two-dimensional nuclear magnetic resonance (2D-NMR) analysis uncovered DHBA-derived benzodioxane structures suggesting that DHB moieties were integrated into the lignin polymer backbone. In addition, up to 40% more glucose was released from transgenic wood following ionic liquid pretreatment and enzymatic hydrolysis. This work highlights the potential of diverting carbon flux from the shikimate pathway for lignin engineering and describes a new type of 'zip-lignin' derived from the incorporation of DHB into poplar lignin.
对生物能源、生物化学和生物材料开发的重新关注，引发了新的策略来工程生物质原料植物中的木质素。本研究首次表明，3,4-二羟基苯甲酸（DHB）与聚合木质素在植物中组装的自由基偶联反应相容。我们将一种细菌 3-脱氢莽草酸脱水酶引入杂种白杨（Populus alba × grandidentata）中，以使碳通量偏离木质素生物合成的莽草酸途径。转基因杨树木材的木质素含量降低了 33%，其中对羟基苯基单元高达 10%。对转基因木材进行温和的碱性水解，释放出的酯键连接的对羟基苯甲酸基团比对照树木少，并且揭示了细胞壁结合的 DHB 以及 3,4-二羟基苯甲酸（DHBA）糖苷的新型掺入。二维核磁共振（2D-NMR）分析揭示了 DHBA 衍生的苯并二氧杂环丁烷结构，表明 DHB 部分被整合到木质素聚合物主链中。此外，在离子液体预处理和酶解后，从转基因木材中释放出高达 40%的更多葡萄糖。这项工作突出了从莽草酸途径转移碳通量用于木质素工程的潜力，并描述了一种源自 DHB 掺入杨树木质素的新型“拉链木质素”。
