Title: Genetic Modification of KNAT7 Transcription Factor Expression Enhances Saccharification and Reduces Recalcitrance of Woody Biomass in Poplars

Abstract

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 KNAT7 gene expression on SCW formation in transgenic poplars, we prepared poplar KNAT7 (PtKNAT7) overexpression (PtKNAT7-OE) and antisense suppression (PtKNAT7-AS) vector constructs for the generation of transgenic poplar lines via Agrobacterium-mediated transformation. Since the overexpression of homologous genes can sometimes result in co-suppression, we also overexpressed Arabidopsis KNAT7 (AtKNAT7-OE) in transgenic poplars. In all these constructs, the expression of KNAT7 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 PtKNAT7-OE and AtKNAT7-OE lines. Yet, no significant increase in lignin content of woody biomass of these transgenic lines was observed. PtKNAT7-AS lines, however, showed reduced expression of many SCW biosynthesis genes downstream of KNAT7 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 KNAT7 knockdown and overexpression transgenic lines than WT controls. These transgenic linesmore » 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 KNAT7 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.« less

Authors:

Ahlawat, Yogesh K. ^[1]; Nookaraju, Akula ^[2]; Harmon-Ware, Anne E. ^[3]; Doeppke, Crissa ^[3]; Biswal, Ajaya K. ^[4]; Joshi, Chandrashekhar P. ^[5]

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+ Show Author Affiliations

1. Michigan Technological Univ., Houghton, MI (United States); Univ. of Florida, Gainesville, FL (United States)
2. Kaveri Seed Company Limited, Secunderabad, (India)
3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
4. Univ. of Georgia, Athens, GA (United States)
5. Michigan Technological Univ., Houghton, MI (United States)

Publication Date:

Tue Oct 26 00:00:00 EDT 2021

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Bioenergy Technologies Office; USDOE Office of Science (SC), Biological and Environmental Research (BER); Ministry of Science and Technology of South Korea

OSTI Identifier:

1835817

Report Number(s):

NREL/JA-2800-80711
Journal ID: ISSN 1664-462X; MainId:77495;UUID:d2d67bc5-94be-47a5-a1bb-fcf527773bcd;MainAdminID:63204

Grant/Contract Number:  

AC36-08GO28308; R31-2009-000-20025-0

Resource Type:

Accepted Manuscript

Journal Name:

Frontiers in Plant Science

Additional Journal Information:

Journal Volume: 12; Journal ID: ISSN 1664-462X

Publisher:

Frontiers Research Foundation

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; antisense; overexpression; saccharification; secondary cell wall biosynthesis; xylem