Genomic Analysis of IRE1-Dependent Decay of Messenger RNAs in Arabidopsis thaliana Reveals a Conection Between Unfolded Protein Response and Several Physiological Plant Process

The unfolded protein response (UPR) is a cellular process triggered by the accumulation of misfolded proteins in the lumen of the endoplasmic reticulum. IRE1 is a transmembrane protein involved in the sensing and signaling during UPR. Signaling by IRE1 requires the cleavage of the AtbZIP60 mRNA in Arabidopsis thaliana. IRE1 cleaves AtbZIP60, producing a processed form of AtbZIP60 that is involved in the regulation of UPR related genes. Arabidopsis thaliana has two copies of IRE1, IRE1a and IRE1b and in addition to AtbZIP60, they can cleave other mRNAs. In order to identify the targets of IRE1a or IRE1b, we performed microarray analysis of wild type and IRE1 double mutant (ire1a ire1b) seedling treated with tunicamicyn (TUN) or dithiothreitol (DTT). Interestingly, we found decay in several transcripts. To confirm the mRNA decay, we performed qPCR analysis of identified transcripts in samples from IRE1 single and double mutant plants treated with tunicamicyn or DTT. Also, we observed a phenotype related to hypocotyl growth in ire1a ire1b plants that is associated to an impaired mRNA decay process. Our data suggest that regulated IRE1-dependet decay of messenger RNAs could be involved in plant cell elongation processes.