Biswal Ajaya K, Atmodjo Melani A, Pattathil Sivakumar, Amos Robert A, Yang Xiaohan, Winkeler Kim, Collins Cassandra, Mohanty Sushree S, Ryno David, Tan Li, Gelineo-Albersheim Ivana, Hunt Kimberly, Sykes Robert W, Turner Geoffrey B, Ziebell Angela, Davis Mark F, Decker Stephen R, Hahn Michael G, Mohnen Debra
1Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602 USA.
3Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd., Athens, GA 30602-4712 USA.
Biotechnol Biofuels. 2018 Jan 17;11:9. doi: 10.1186/s13068-017-1002-y. eCollection 2018.
The development of fast-growing hardwood trees as a source of lignocellulosic biomass for biofuel and biomaterial production requires a thorough understanding of the plant cell wall structure and function that underlie the inherent recalcitrance properties of woody biomass. Downregulation of in was recently reported to result in improved biomass saccharification, plant growth, and biomass yield. To further understand function in biomass recalcitrance and plant growth, here we report the effects of overexpression in .
Increasing transcript expression by 7-49% in -overexpression (OE) lines resulted in a nearly complete opposite biomass saccharification and plant growth phenotype to that observed previously in -knockdown (KD) lines. This included significantly reduced glucose, xylose, and total sugar release (12-13%), plant height (6-54%), stem diameter (8-40%), and overall total aerial biomass yield (48-61%) in 3-month-old, greenhouse-grown -OE lines compared to controls. Total lignin content was unaffected by the gene overexpression. Importantly, selected -OE lines retained the recalcitrance and growth phenotypes upon growth for 9 months in the greenhouse and 2.8 years in the field. -OE plants had significantly smaller leaves with lower relative water content, and significantly reduced stem wood xylem cell numbers and size. At the cell wall level, xylose and galacturonic acid contents increased markedly in total cell walls as well as in soluble and insoluble cell wall extracts, consistent with increased amounts of xylan and homogalacturonan in the -OE lines. This led to increased cell wall recalcitrance, as manifested by the 9-15% reduced amounts of recovered extractable wall materials and 8-15% greater amounts of final insoluble pellet in the -OE lines compared to controls.
The combined phenotype and chemotype data from -OE and -KD transgenics clearly establish as a recalcitrance- and growth-associated gene in poplar. Overall, the data support the hypothesis that GAUT12.1 synthesizes either an HG-containing primer for xylan synthesis or an HG glycan required for proper xylan deposition, anchoring, and/or architecture in the wall, and the possibility of HG and xylan glycans being connected to each other by a base-sensitive covalent linkage.
快速生长的硬木树作为用于生物燃料和生物材料生产的木质纤维素生物质来源的开发，需要深入了解构成木质生物质固有难降解特性基础的植物细胞壁结构和功能。最近报道，[基因名称]的下调导致生物质糖化、植物生长和生物质产量得到改善。为了进一步了解[基因名称]在生物质难降解性和植物生长中的功能，我们在此报告了[基因名称]在[植物名称]中过表达的影响。
在[植物名称]过表达（OE）系中，[基因名称]转录本表达增加7%-49%，导致生物质糖化和植物生长表型与之前在[基因名称]敲低（KD）系中观察到的几乎完全相反。这包括与对照相比，3个月大的温室种植的[植物名称]OE系中葡萄糖、木糖和总糖释放量显著降低（12%-13%），株高降低（6%-54%），茎直径降低（8%-40%），以及总地上生物量产量降低（48%-61%）。总木质素含量不受基因过表达的影响。重要的是，所选的[植物名称]OE系在温室中生长9个月和在田间生长2.8年后仍保留难降解性和生长表型。[植物名称]OE植株的叶片明显较小，相对含水量较低，茎木质部细胞数量和大小显著减少。在细胞壁水平上，总细胞壁以及可溶性和不溶性细胞壁提取物中的木糖和半乳糖醛酸含量显著增加，这与[植物名称]OE系中木聚糖和同型半乳糖醛酸含量的增加一致。这导致细胞壁难降解性增加，表现为与对照相比，[植物名称]OE系中可回收的可提取壁材料量减少9%-15%，最终不溶性沉淀量增加8%-15%。
来自[植物名称]OE和[植物名称]KD转基因植株的综合表型和化学类型数据清楚地表明[基因名称]是杨树中与难降解性和生长相关的基因。总体而言，这些数据支持以下假设：GAUT12.1合成用于木聚糖合成的含HG引物或壁中木聚糖正确沉积、锚定和/或结构所需的HG聚糖，以及HG和木聚糖聚糖通过碱基敏感的共价键相互连接的可能性。
