Ahlawat Yogesh Kumar, Nookaraju Akula, Harman-Ware Anne E, Doeppke Crissa, Biswal Ajaya K, Joshi Chandrashekhar P
Department of Biological Sciences, Michigan Technological University, Houghton, MI, United States.
Department of Horticultural Sciences, University of Florida, Gainesville, FL, United States.
Front Plant Sci. 2021 Oct 26;12:762067. doi: 10.3389/fpls.2021.762067. eCollection 2021.
The precise role of KNAT7 transcription factors (TFs) in regulating secondary cell wall (SCW) biosynthesis in poplars has remained unknown, while our understanding of KNAT7 functions in other plants is continuously evolving. To study the impact of genetic modifications of homologous and heterologous gene expression on SCW formation in transgenic poplars, we prepared poplar () overexpression (-OE) and antisense suppression (-AS) vector constructs for the generation of transgenic poplar lines -mediated transformation. Since the overexpression of homologous genes can sometimes result in co-suppression, we also overexpressed () in transgenic poplars. In all these constructs, the expression of transgenes was driven by developing xylem (DX)-specific promoter, DX15. Compared to wild-type (WT) controls, many SCW biosynthesis genes downstream of KNAT7 were highly expressed in poplar and lines. Yet, no significant increase in lignin content of woody biomass of these transgenic lines was observed. lines, however, showed reduced expression of many SCW biosynthesis genes downstream of accompanied by a reduction in lignin content of wood compared to WT controls. Syringyl to Guaiacyl lignin (S/G) ratios were significantly increased in all three knockdown and overexpression transgenic lines than WT controls. These transgenic lines were essentially indistinguishable from WT controls in terms of their growth phenotype. Saccharification efficiency of woody biomass was significantly increased in all transgenic lines than WT controls. Overall, our results demonstrated that developing xylem-specific alteration of expression affects the expression of SCW biosynthesis genes, impacting at least the lignification process and improving saccharification efficiency, hence providing one of the powerful tools for improving bioethanol production from woody biomass of bioenergy crops and trees.
KNAT7转录因子（TFs）在调控杨树次生细胞壁（SCW）生物合成中的精确作用尚不清楚，而我们对KNAT7在其他植物中的功能的理解正在不断发展。为了研究同源和异源基因表达的遗传修饰对转基因杨树SCW形成的影响，我们制备了杨树（）过表达（-OE）和反义抑制（-AS）载体构建体，用于通过介导转化产生转基因杨树品系。由于同源基因的过表达有时会导致共抑制，我们还在转基因杨树中过表达了（）。在所有这些构建体中，转基因的表达由发育中的木质部（DX）特异性启动子DX15驱动。与野生型（WT）对照相比，KNAT7下游的许多SCW生物合成基因在杨树和品系中高表达。然而，未观察到这些转基因品系的木质生物质中木质素含量有显著增加。然而，与WT对照相比，品系中许多下游SCW生物合成基因的表达降低，同时木材中木质素含量也降低。在所有三个敲低和过表达转基因品系中，丁香基与愈创木基木质素（S/G）比率均显著高于WT对照。这些转基因品系在生长表型方面与WT对照基本没有区别。所有转基因品系的木质生物质糖化效率均显著高于WT对照。总体而言，我们的结果表明，发育中的木质部特异性改变的表达会影响SCW生物合成基因的表达，至少影响木质化过程并提高糖化效率，从而为提高生物能源作物和树木的木质生物质生产生物乙醇提供了有力工具之一。
