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Research article - Peer-reviewed, 2023

Xylan glucuronic acid side chains fix suberin-like aliphatic compounds to wood cell walls

Derba-Maceluch, Marta; Mitra, Madhusree; Hedenstrom, Mattias; Liu, Xiaokun; Gandla, Madhavi L.; Barbut, Felix R.; Abreu, Ilka N.; Donev, Evgeniy N.; Urbancsok, Janos; Moritz, Thomas; Jonsson, Leif J.; Tsang, Adrian; Powlowski, Justin; Master, Emma R.; Mellerowicz, Ewa J.

Abstract

Wood is the most important repository of assimilated carbon in the biosphere, in the form of large polymers (cellulose, hemicelluloses including glucuronoxylan, and lignin) that interactively form a composite, together with soluble extractives including phenolic and aliphatic compounds. Molecular interactions among these compounds are not fully understood.We have targeted the expression of a fungal alpha-glucuronidase to the wood cell wall of aspen (Populus tremula L. x tremuloides Michx.) and Arabidopsis (Arabidopsis thaliana (L.) Heynh), to decrease contents of the 4-O-methyl glucuronopyranose acid (mGlcA) substituent of xylan, to elucidate mGlcA's functions.The enzyme affected the content of aliphatic insoluble cell wall components having composition similar to suberin, which required mGlcA for binding to cell walls. Such suberin-like compounds have been previously identified in decayed wood, but here, we show their presence in healthy wood of both hardwood and softwood species. By contrast, gamma-ester bonds between mGlcA and lignin were insensitive to cell wall-localized alpha-glucuronidase, supporting the intracellular formation of these bonds.These findings challenge the current view of the wood cell wall composition and reveal a novel function of mGlcA substituent of xylan in fastening of suberin-like compounds to cell wall. They also suggest an intracellular initiation of lignin-carbohydrate complex assembly.

Keywords

lignin-carbohydrate complexes; Populus; saccharification; suberin; wood cell wall; xylan

Published in

New Phytologist
2023, Volume: 238, number: 1, pages: 297-312
Publisher: WILEY