Bhatia Rakesh, Timms-Taravella Emma, Roberts Luned A, Moron-Garcia Odin M, Hauck Barbara, Dalton Sue, Gallagher Joe A, Wagner Moritz, Clifton-Brown John, Bosch Maurice
Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Plas Gogerddan, Aberystwyth, SY23 3EE, UK.
Department of Agronomy and Plant Breeding, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany.
Biotechnol Biofuels Bioprod. 2023 Feb 22;16(1):29. doi: 10.1186/s13068-023-02279-2.
Perennial C grasses from the genus Miscanthus are widely regarded as leading and promising dedicated bioenergy crops due to their high biomass accumulation on marginal land with low environmental impacts and maintenance requirements over its productive life. There is an urgent socio-political and environmental need to ramp up the production of alternative, affordable and green bioenergy sources and to re-direct the net zero carbon emissions trajectory. Hence, up-scaling of Miscanthus cultivation as a source of biomass for renewable energy could play an important role to strategically address sustainable development goals for a growing bio-based economy. Certain Miscanthus sinensis genotypes are particularly interesting for their biomass productivity across a wide range of locations. As the aromatic biomass component lignin exhibits a higher energy density than cell wall polysaccharides and is generally used as an indicator for heating or calorific value, genetic engineering could be a feasible strategy to develop M. sinensis biomass with increased lignin content and thus improving the energetic value of the biomass.
For this purpose, transgenic M. sinensis were generated by Agrobacterium-mediated transformation for expression of ZmMYB167, a MYB transcription factor known for regulating lignin biosynthesis in C and C grasses. Four independent transgenic ZmMYB167 Miscanthus lines were obtained. Agronomic traits such as plant height, tillering and above-ground dry weight biomass of the transgenic plants were not different to that of wild-type control plants. Total lignin content of the transgenic plants was ~ 15-24% higher compared with control plants. However, the structural carbohydrates, glucan and xylan, were decreased by ~ 2-7% and ~ 8-10%, respectively, in the transgenic plants. Moreover, expression of ZmMYB167 in transgenic plants did not alter lignin composition, phenolic compounds or enzymatic saccharification efficiency yields but importantly improved total energy levels in Miscanthus biomass, equivalent to 10% higher energy yield per hectare.
This study highlights ZmMYB167 as a suitable target for genetic lignin bioengineering interventions aimed at advancing and developing lignocellulosic biomass supply chains for sustainable production of renewable bioenergy.
芒属多年生C4草本植物因其在边际土地上能积累大量生物量，且在其整个生产周期内对环境影响小、维护要求低，而被广泛视为领先且有前景的专用生物能源作物。在社会政治和环境方面，迫切需要增加替代的、经济实惠且绿色的生物能源生产，并重新引导净零碳排放轨迹。因此，扩大芒草种植作为可再生能源的生物质来源，对于战略性地实现不断发展的生物基经济的可持续发展目标可能发挥重要作用。某些芒草基因型因其在广泛区域的生物质生产力而特别受关注。由于芳香生物质成分木质素的能量密度高于细胞壁多糖，且通常用作加热或热值的指标，基因工程可能是一种可行的策略，用于培育木质素含量增加的芒草生物质，从而提高生物质的能量价值。
为此，通过农杆菌介导的转化方法培育了转基因芒草，用于表达ZmMYB167，这是一种已知在C4和C3禾本科植物中调节木质素生物合成的MYB转录因子。获得了四个独立的ZmMYB167转基因芒草株系。转基因植物的农艺性状，如株高、分蘖和地上干重生物量，与野生型对照植物没有差异。转基因植物的总木质素含量比对照植物高约15 - 24%。然而，转基因植物中的结构性碳水化合物葡聚糖和木聚糖分别减少了约2 - 7%和约8 - 10%。此外，ZmMYB167在转基因植物中的表达没有改变木质素组成、酚类化合物或酶促糖化效率，但重要的是提高了芒草生物质中的总能量水平，相当于每公顷能量产量提高了10%。
本研究强调ZmMYB167是基因木质素生物工程干预的合适靶点，旨在推进和发展木质纤维素生物质供应链，以实现可再生生物能源的可持续生产。
