Wood forming tissue‐specific bicistronic expression of PdGA20ox1 and PtrMYB221 improves both the quality and quantity of woody biomass production in a hybrid poplar

First author: Jin‐Seong Cho; Affiliations: Kyung Hee University (韩国庆熙大学): Yongin, Korea

Corresponding author: Jae‐Heung Ko

With the exponential growth of the human population and industrial developments, research on renewable energy resources is required to alleviate (缓和) environmental and economic impacts caused by the consumption of fossil fuels (化石燃料). In this study, we present a synthetic biological application of a wood forming tissue‐specific bicistronic (双顺反子) gene expression system to improve both the quantity and quality of woody biomass to minimize undesirable growth penalties (害处). Our transgenic poplars, designed to express both PdGA20ox1 (a GA20‐oxidase (氧化酶) from Pinus densiflora (赤松) producing bioactive gibberellin, GA) and PtrMYB221 (a MYB transcription factor negatively regulating lignin biosynthesis) under the developing xylem (DX) tissue‐specific promoter (i.e., DX15::PdGA20ox1‐2A‐PtrMYB221 poplar), resulted in a 2‐fold increase in biomass quantity compared to wild‐ ype (WT), without undesirable growth defects. A similar phenotype was observed in transgenic Arabidopsis plants harboring the same gene constructs. These phenotypic consequences were further verified in the field experiments. Importantly, our transgenic poplars exhibited an improved quality of biomass with reduced lignin content (~16.0 wt%) but increased holocellulose (综纤维素) content (~6.6 wt%). Furthermore, the saccharification efficiency (糖化效率) of our transgenic poplar increased significantly by up to 8%. Our results demonstrate that the controlled production of both GA and a secondary wall modifying regulator in the same spatio‐ emporal manner can be utilized as an efficient biotechnological tool for producing the desired multi‐purpose woody biomass.

随着人类人口的快速增长和工业的发展，寻找再生新能源缓解由化石燃料引起的环境和经济问题成为越来越急迫的需求。本文中，作者通过木质部组织特异性的双顺反子基因表达系统以同时提升木材生物量的数量和质量，同时最小化生长缺陷。作者将赤松中合成赤霉素的GA20-氧化酶PdGA20ox1基因以及负调控木质素生物合成转录因子PtrMYB221基因连接到发育中的韧皮部组织特异性启动子（DX15::PdGA20ox1‐2A‐PtrMYB221）转到杨树中，结果相比于野生型，转基因的杨树生物量提升2倍，并且没有不良的生长缺陷。作者在转同样基因的拟南芥中也观测到了相似的表型。作者进一步在田间试验中验证了这些表型的稳定性。重要的是，作者构建的转基因杨树生物量的质量获得了提升，其中木质素含量降低了16%，综纤维素的含量增加6.6%。此外，转基因杨树的糖化效率增加了8%。本文的结果显示可以通过整合GA生物合成和次生细胞壁调控因子的时空表达来满足木材生物量提升的多方面需求。

doi: https://doi.org/10.1111/pbi.13036

Journal: Plant Biotechnology Journal

First Published: 05 December, 2018