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Research article - Peer-reviewed, 2020

Cell Wall Acetylation in Hybrid Aspen Affects Field Performance, Foliar Phenolic Composition and Resistance to Biological Stress Factors in a Construct-Dependent Fashion

Derba-Maceluch, Marta; Amini, Fariba; Donev, Evgeniy; Mohan Pawar, Prashant; Michaud, Lisa; Johansson, Ulf; Albrectsen, Benedicte R.; Mellerowicz, Ewa

Abstract

The production of biofuels and "green" chemicals from the lignocellulose of fast-growing hardwood species is hampered by extensive acetylation of xylan. Different strategies have been implemented to reduce xylan acetylation, resulting in transgenic plants that show good growth in the greenhouse, improved saccharification and fermentation, but the field performance of such plants has not yet been reported. The aim of this study was to evaluate the impact of reduced acetylation on field productivity and identify the best strategies for decreasing acetylation. Growth and biological stress data were evaluated for 18 hybrid aspen lines with 10-20% reductions in the cell wall acetyl content from a five year field experiment in Southern Sweden. The reduction in acetyl content was achieved either by suppressing the process of acetylation in the Golgi by reducing expression of REDUCED WALL ACETYLATION (RWA) genes, or by post-synthetic acetyl removal by fungal acetyl xylan esterases (AXEs) from two different families, CE1 and CE5, targeting them to cell walls. Transgene expression was regulated by either a constitutive promoter (35S) or a wood-specific promoter (WP). For the majority of transgenic lines, growth was either similar to that in WT and transgenic control (WP:GUS) plants, or slightly reduced. The slight reduction was observed in the AXE-expressing lines regulated by the 35S promoter, not those with the WP promoter which limits expression to cells developing secondary walls. Expressing AXEs regulated by the 35S promoter resulted in increased foliar arthropod chewing, and altered condensed tannins and salicinoid phenolic glucosides (SPGs) profiles. Greater growth inhibition was observed in the case of CE5 than with CE1 AXE, and it was associated with increased foliar necrosis and distinct SPG profiles, suggesting that CE5 AXE could be recognized by the pathogen-associated molecular pattern system. For each of three different constructs, there was a line with dwarfism and growth abnormalities, suggesting random genetic/epigenetic changes. This high frequency of dwarfism (17%) is suggestive of a link between acetyl metabolism and chromatin function. These data represent the first evaluation of acetyl-reduced plants from the field, indicating some possible pitfalls, and identifying the best strategies, when developing highly productive acetyl-reduced feedstocks.

Keywords

Populus tremula x tremuloides; transgenic trees; field trial; biotic resistance; salicinoid phenolic glucosides; condensed tannins; HjAXE; AnAXE1

Published in

Frontiers in Plant Science
2020, volume: 11, article number: 651

Authors' information

Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology
Amini, Fariba
Umea University
Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology
Mohan Pawar, Prashant
Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology
Michaud, Lisa
Umeå University
Swedish University of Agricultural Sciences, Unit for Field-based Forest Research
Albrectsen, Benedicte R.
Umea University
Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology

Associated SLU-program

SLU Network Plant Protection

UKÄ Subject classification

Plant Biotechnology

Publication Identifiers

DOI: https://doi.org/10.3389/fpls.2020.00651

URI (permanent link to this page)

https://res.slu.se/id/publ/106508