Role of extensin arabinosylation in root defence

Extensins are hydroxyproline-rich glycoproteins thought to strengthen the plant cell wall, one of the first barriers against pathogens, through intra- and intermolecular cross-links. The glycan moiety of extensins is believed to confer the correct structural conformation to the glycoprotein, leading to self-assembly within the cell wall that helps limit microbial adherence and invasion. However, this role is not clearly established.

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Castilleux et al. used Arabidopsis thaliana mutants impaired in extensin arabinosylation to investigate the role of extensin arabinosylation in root–microbe interactions. Mutant and wild-type roots were stimulated to elicit an immune response with flagellin 22 and immunolabelled with a set of anti-extensin antibodies. Roots were also inoculated with a soilborne oomycete, Phytophthora parasitica, to assess the effect of extensin arabinosylation on root colonization.

The authors provide evidence for a link between extensin arabinosylation and root defence, and propose a model to explain the importance of glycosylation in limiting invasion of root cells by pathogenic oomycetes.

Further reading

Castilleux, R., Plancot, B., Gügi, B., Attard, A., Loutelier-Bourhis, C., Lefranc, B., … Vicré, M. (2019). Extensin arabinosylation is involved in root response to elicitors and limits oomycete colonization. Annals of Botany. https://doi.org/10.1093/aob/mcz068