Unfolded protein-independent IRE1 activation contributes to multifaceted developmental processes in Arabidopsis

Life Sci Alliance. 2019 Oct 10;2(5):e201900459. doi: 10.26508/lsa.201900459. Print 2019 Oct.


In Arabidopsis, the IRE1A and IRE1B double mutant (ire1a/b) is unable to activate cytoplasmic splicing of bZIP60 mRNA and regulated IRE1-dependent decay under ER stress, whereas the mutant does not exhibit severe developmental defects under normal conditions. In this study, we focused on the Arabidopsis IRE1C gene, whose product lacks a sensor domain. We found that the ire1a/b/c triple mutant is lethal, and heterozygous IRE1C (ire1c/+) mutation in the ire1a/b mutants resulted in growth defects and reduction of the number of pollen grains. Genetic analysis revealed that IRE1C is required for male gametophyte development in the ire1a/b mutant background. Expression of a mutant form of IRE1B that lacks the luminal sensor domain (ΔLD) complemented a developmental defect in the male gametophyte in ire1a/b/c haplotype. In vivo, the ΔLD protein was activated by glycerol treatment that increases the composition of saturated lipid and was able to activate regulated IRE1-dependent decay but not bZIP60 splicing. These observations suggest that IRE1 contributes to plant development, especially male gametogenesis, using an alternative activation mechanism that bypasses the unfolded protein-sensing luminal domain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics*
  • Gametogenesis, Plant
  • Gene Expression Regulation, Developmental / drug effects
  • Gene Expression Regulation, Plant / drug effects
  • Genes, Lethal
  • Glycerol / pharmacology
  • Intracellular Signaling Peptides and Proteins / genetics*
  • Mutation
  • Pollen / genetics
  • Pollen / growth & development
  • Protein Domains
  • Protein Kinases / chemistry
  • Protein Kinases / genetics*
  • RNA Stability
  • RNA, Plant / genetics
  • Unfolded Protein Response*


  • AT3G11870 protein, Arabidopsis
  • Arabidopsis Proteins
  • Intracellular Signaling Peptides and Proteins
  • RNA, Plant
  • Protein Kinases
  • Ire1-1 protein, Arabidopsis
  • Ire1-2 protein, Arabidopsis
  • Glycerol