Bewg William P, Poovaiah Charleson, Lan Wu, Ralph John, Coleman Heather D
Queensland University of Technology, Brisbane, QLD 4000 Australia.
Department of Biology, Syracuse University, Syracuse, NY 13244 USA.
Biotechnol Biofuels. 2016 Dec 20;9:270. doi: 10.1186/s13068-016-0683-y. eCollection 2016.
Sugarcane is a subtropical crop that produces large amounts of biomass annually. It is a key agricultural crop in many countries for the production of sugar and other products. Residual bagasse following sucrose extraction is currently underutilized and it has potential as a carbohydrate source for the production of biofuels. As with all lignocellulosic crops, lignin acts as a barrier to accessing the polysaccharides, and as such, is the focus of transgenic efforts. In this study, we used RNAi to individually reduce the expression of three key genes in the lignin biosynthetic pathway in sugarcane. These genes, caffeoyl-CoA -methyltransferase (), ferulate 5-hydroxylase () and caffeic acid -methyltransferase (), impact lignin content and/or composition.
For each RNAi construct, we selected three events for further analysis based on qRT-PCR results. For the lines, there were no lines with a reduction in lignin content and only one line showed improved glucose release. For , no lines had reduced lignin, but one line had a significant increase in glucose release. For , one line had reduced lignin content, and this line and another released higher levels of glucose during enzymatic hydrolysis. Two of the lines with improved glucose release (F5H-2 and COMT-2) also had reduced S:G ratios.
Along with improvements in bagasse quality for the production of lignocellulosic-based fuels, there was only one line with reduction in juice sucrose extraction, and three lines with significantly improved sucrose production, providing evidence that the alteration of sugarcane for improved lignocellulosic ethanol production can be achieved without negatively impacting sugar production and perhaps even enhancing it.
甘蔗是一种亚热带作物，每年产生大量生物质。它是许多国家用于生产糖和其他产品的关键农作物。蔗糖提取后剩余的甘蔗渣目前未得到充分利用，它有潜力作为生产生物燃料的碳水化合物来源。与所有木质纤维素作物一样，木质素是获取多糖的障碍，因此是转基因研究的重点。在本研究中，我们使用RNA干扰分别降低甘蔗木质素生物合成途径中三个关键基因的表达。这些基因，咖啡酰辅酶A -甲基转移酶（）、阿魏酸5 -羟化酶（）和咖啡酸 -甲基转移酶（），会影响木质素含量和/或组成。
对于每个RNA干扰构建体，我们根据qRT-PCR结果选择了三个事件进行进一步分析。对于 系，没有木质素含量降低的株系，只有一个株系显示葡萄糖释放有所改善。对于 ，没有株系的木质素减少，但有一个株系的葡萄糖释放显著增加。对于 ，有一个株系的木质素含量降低，并且该株系和另一个株系在酶水解过程中释放出更高水平的葡萄糖。两个葡萄糖释放改善的株系（F5H - 2和COMT - 2）的S:G比值也降低了。
除了改善甘蔗渣质量以生产基于木质纤维素的燃料外，只有一个株系的蔗汁蔗糖提取量减少，三个株系的蔗糖产量显著提高，这证明在不负面影响糖产量甚至可能提高糖产量的情况下，可以实现甘蔗改良以提高木质纤维素乙醇产量。
