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

Yutao Zou, Nora Gigli-Bisceglia, Eva van Zelm, Pinelopi Kokkinopoulou, Magdalena Julkowska, Maarten Besten, Thu-Phuong Nguyen, Hongfei Li, Jasper Lamers, Thijs de Zeeuw, Joram Dongus, Yuxiao Zeng, Yu Cheng, Iko Koevoets, Bodil Jørgensen, Marcel Giesbers, Jelmer Vroom, Tijs Ketelaar, Bent L. Petersen, Timo EngelsdorfJoris Sprakel, Yanxia Zhang, Christa Testerink

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

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.
Original languageEnglish
Article numberkoae135
JournalThe Plant Cell
DOIs
Publication statusE-pub ahead of print - 1 May 2024

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