Overexpression of PtoMYB115 improves lignocellulose recalcitrance to enhance biomass digestibility and bioethanol yield by specifically regulating lignin biosynthesis in transgenic poplar

Abstract

Background Woody plants provide the most abundant biomass resource that is convertible for biofuels. Since lignin is a crucial recalcitrant factor against lignocellulose hydrolysis, genetic engineering of lignin biosynthesis is considered as a promising solution. Many MYB transcription factors have been identified to involve in the regulation of cell wall formation or phenylpropanoid pathway. In a previous study, we identified that PtoMYB115 contributes to the regulation of proanthocyanidin pathway, however, little is known about its role in lignocellulose biosynthesis and biomass saccharification in poplar. Results Here, we detected the changes of cell wall features and examined biomass enzymatic saccharification for bioethanol production under various chemical pretreatments in PtoMYB115 transgenic plants. We reported that PtoMYB115 might specifically regulate lignin biosynthesis to affect xylem development. Overexpression of PtoMYB115 altered lignin biosynthetic gene expression, resulting in reduced lignin deposition, raised S/G and beta-O-4 linkage, resulting in a significant reduction in cellulase adsorption with lignin and an increment in cellulose accessibility. These alterations consequently improved lignocellulose recalcitrance for significantly enhanced biomass saccharification and bioethanol yield in the PtoMYB115-OE transgenic lines. In contrast, the knockout of PtoMYB115 by CRISPR/Cas9 showed reduced woody utilization under various chemical pretreatments. Conclusions This study shows that PtoMYB115 plays an important role in specifically regulating lignin biosynthesis and improving lignocellulose features. The enhanced biomass saccharification and bioethanol yield in the PtoMYB115-OE lines suggests that PtoMYB115 is a candidate gene for genetic modification to facilitate the utilization of biomass.

Comparative study of acid- and alkali-catalyzed 1,4-butanediol pretreatment for co-production of fermentable sugars and value-added lignin compounds

“…It was considered the proper cellulose accessibility that resulted from hemicellulose solubilization and lignin removal played a primary role in affecting the enzymatic digestibility of biomass [ 29 ]. Other than lignin removal and hemicellulose solubilization, the physiochemical properties of substrate were also considered to play an important role.…”

Wood of trees: Cellular structure, molecular formation, and genetic engineering

“…Overexpression of AtMYB46 , which is directly downstream of SND1 in the regulatory network for SCW biosynthesis, resulted in a lower lignin S/G ratio and acetylated hemicellulose in Populus (Nakano et al, 2022). MYB115 overexpression decreased lignin quantity and increased the S/G ratio, which improved saccharification and bioethanol yield (Fan et al, 2022). Similarly, KNAT7 overexpression reduced lignin amounts while increasing the S/G ratio and saccharification efficiency (Ahlawat et al, 2021).…”