PT  - JOURNAL ARTICLE
AU  - Mishiba, Kei-ichiro
AU  - Iwata, Yuji
AU  - Mochizuki, Tomofumi
AU  - Matsumura, Atsushi
AU  - Nishioka, Nanami
AU  - Hirata, Rikako
AU  - Koizumi, Nozomu
TI  - Unfolded protein-independent IRE1 activation contributes to multifaceted developmental processes in Arabidopsis
AID  - 10.26508/lsa.201900459
DP  - 2019 Oct 01
TA  - Life Science Alliance
PG  - e201900459
VI  - 2
IP  - 5
4099  - http://www.life-science-alliance.org/content/2/5/e201900459.short
4100  - http://www.life-science-alliance.org/content/2/5/e201900459.full
SO  - Life Sci. Alliance2019 Oct 01; 2
AB  - 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.