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The unfolded protein response modulates a phosphoinositide-binding protein through the IRE1-bZIP60 pathway.

  • Yu, Chao-Yuan1
  • Kanehara, Kazue2
  • 1 Academia Sinica CITY: Taipei Taiwan. , (Taiwan)
  • 2 Academia Sinica CITY: Taipei POSTAL_CODE: 11529 Taiwan [email protected] , (Taiwan)
Published Article
Plant physiology
Publication Date
Mar 23, 2020
DOI: 10.1104/pp.19.01488
PMID: 32205450


Phosphoinositides function as lipid signals in plant development and stress tolerance by binding with partner proteins. We previously reported that Arabidopsis (Arabidopsis thaliana) phosphoinositide-specific phospholipase C2 (PLC2) functions in the endoplasmic reticulum (ER) stress response. However, the underlying molecular mechanisms of how phosphoinositides act in the ER stress response remain elusive. Here, we report that a phosphoinositide-binding protein, SMALLER TRICHOMES WITH VARIABLE BRANCHES (SVB), is involved in the ER stress tolerance. SVB contains a DUF538 domain with unknown function; orthologs are exclusively found in Viridiplantae (green plants). We established that SVB is ubiquitously expressed in plant tissues and is localized to the ER, Golgi apparatus, prevacuolar compartment, and plasma membranes. The knockout mutants of svb showed enhanced tolerance to ER stress, which was genetically complemented by transducing genomic SVB. SVB showed time-dependent induction after tunicamycin-induced ER stress, which depended on IRE1 and bZIP60 but not bZIP17 and bZIP28 in the unfolded protein response (UPR). A protein-lipid overlay assay showed specific binding of SVB to phosphatidylinositol 3,5-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate. SVB is therefore suggested to be the plant-specific phosphoinositide-binding protein whose expression is controlled by the UPR through the IRE1-bZIP60 pathway in Arabidopsis. {copyright, serif} 2020 American Society of Plant Biologists. All rights reserved.

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