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Hydroxycinnamic acid-modified xylan side chains and their cross-linking products in rice cell walls are reduced in the Xylosyl arabinosyl substitution of xylan 1 mutant.

Published version
Peer-reviewed

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Authors

Feijao, Carolina 
Morreel, Kris 
Anders, Nadine 
Tryfona, Theodora 
Busse-Wicher, Marta 

Abstract

The intricate architecture of cell walls and the complex cross-linking of their components hinders some industrial and agricultural applications of plant biomass. Xylan is a key structural element of grass cell walls, closely interacting with other cell wall components such as cellulose and lignin. The main branching points of grass xylan, 3-linked l-arabinosyl substitutions, can be modified by ferulic acid (a hydroxycinnamic acid), which cross-links xylan to other xylan chains and lignin. XAX1 (Xylosyl arabinosyl substitution of xylan 1), a rice (Oryza sativa) member of the glycosyltransferase family GT61, has been described to add xylosyl residues to arabinosyl substitutions modified by ferulic acid. In this study, we characterize hydroxycinnamic acid-decorated arabinosyl substitutions present on rice xylan and their cross-linking, in order to decipher the role of XAX1 in xylan synthesis. Our results show a general reduction of hydroxycinnamic acid-modified 3-linked arabinosyl substitutions in xax1 mutant rice regardless of their modification with a xylosyl residue. Moreover, structures resembling the direct cross-link between xylan and lignin (ferulated arabinosyl substitutions bound to lignin monomers and dimers), together with diferulates known to cross-link xylan, are strongly reduced in xax1. Interestingly, apart from feruloyl and p-coumaroyl modifications on arabinose, putative caffeoyl and oxalyl modifications were characterized, which were also reduced in xax1. Our results suggest an alternative function of XAX1 in the transfer of hydroxycinnamic acid-modified arabinosyl substitutions to xylan, rather than xylosyl transfer to arabinosyl substitutions. Ultimately, XAX1 plays a fundamental role in cross-linking, providing a potential target for the improvement of use of grass biomass.

Description

Keywords

Glycosyltransferase family 61, Oryza sativa, arabinosyltransferase, hydroxycinnamic acid, lignin, xylan, xylosyl arabinosyl substitution of xylan 1, Cell Wall, Coumaric Acids, Lignin, Oryza, Poaceae, Xylans

Journal Title

Plant J

Conference Name

Journal ISSN

0960-7412
1365-313X

Volume Title

Publisher

Wiley
Sponsorship
Biotechnology and Biological Sciences Research Council (BB/K005537/1)
Biotechnology and Biological Sciences Research Council (BB/J014540/1)
Biotechnology and Biological Sciences Research Council (BB/F013434/1)