Characterization of a plant-specific gene induced by endoplasmic reticulum stress in Arabidopsis thaliana.

We have conducted transcriptome analysis and have identified a number of genes that are upregulated by treatment with the endoplasmic reticulum (ER) stress inducer tunicamycin. Here we focused on one particular gene of unknown function. This gene, designated tunicamycin induced 1 (TIN1), encodes an open reading frame consisting of 424 amino acids with a putative signal peptide. TIN1 orthologs are present in several plant species, including poplar, rice, and moss, but not in other organisms, including yeast and animals. Transcriptional induction of TIN1 by ER stress was regulated in part by AtbZIP60, a membrane-bound transcription factor activating many ER stress-responsive genes. In agreement with increases of TIN1 transcripts, the TIN1 protein accumulated in response to tunicamycin treatment. It was localized at the ER when fused with a fluorescent protein. These results represent a first step toward elucidating the molecular function of TIN1.