Arabinosylation of cell wall extensin is required for the directional response to salinity in roots

Soil salinity is a major contributor to crop yield losses. To improve our understanding of root responses to salinity, we developed and exploited a real-time salt-induced tilting assay. This assay follows root growth upon both gravitropic and salt challenges, revealing that root bending upon tilting is modulated by Na+ ions, but not by osmotic stress. Next, we measured this salt-specific response in 345 natural Arabidopsis (Arabidopsis thaliana) accessions and discovered a genetic locus, encoding the cell wall–modifying enzyme EXTENSIN ARABINOSE DEFICIENT TRANSFERASE (ExAD) that is associated with root bending in the presence of NaCl (hereafter salt). Extensins are a class of structural cell wall glycoproteins known as hydroxyproline (Hyp)-rich glycoproteins, which are posttranslationally modified by O-glycosylation, mostly involving Hyp-arabinosylation. We show that salt-induced ExAD-dependent Hyp-arabinosylation influences root bending responses and cell wall thickness. Roots of exad1 mutant seedlings, which lack Hyp-arabinosylation of extensin, displayed increased thickness of root epidermal cell walls and greater cell wall porosity. They also showed altered gravitropic root bending in salt conditions and a reduced salt-avoidance response. Our results suggest that extensin modification via Hyp-arabinosylation is a unique salt-specific cellular process required for the directional response of roots exposed to salinity.

Bibliographic Details

Main Authors:	Zou, Yutao, Gigli-Bisceglia, Nora, van Zelm, Eva, Kokkinopoulou, Pinelopi, Julkowska, Magdalena, Besten, Maarten, Nguyen, Thu-Phuong, Li, Hongfei, Lamers, Jasper, de Zeeuw, Thijs, Dongus, Joram, Zeng, Yuxiao, Cheng, Yu, Koevoets, Iko, Jørgensen, Bodil, Giesbers, Marcel, Vroom, Jelmer, Ketelaar, Tijs, Petersen, Bent L., Engelsdorf, Timo, Sprakel, Joris, Zhang, Yanxia, Testerink, Christa
Format:	Article/Letter to editor biblioteca
Language:	English
Subjects:	Life Science,
Online Access:	https://research.wur.nl/en/publications/arabinosylation-of-cell-wall-extensin-is-required-for-the-directi
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