Transcriptional regulation of an Arabidopsis gene encoding a CCT domain-containing protein during endoplasmic reticulum stress

Abstract

In eukaryotic cells, accumulation of unfolded proteins in the endoplasmic reticulum (ER) triggers the transcriptional induction of ER-resident molecular chaperones and folding enzymes to maintain cellular homeostasis, termed the ER stress response or the unfolded protein response (UPR). In this study we focused on a putative transcriptional regulator of Arabidopsis thaliana whose transcripts accumulate in response to the ER stress inducer tunicamycin. This gene, designated as TCR1 (tunicamycin-induced CONSTANS-like-related 1), encodes a predicted protein of 195 amino acids with a plant-specific CCT (CONSTANS, CONSTANS-like, TOC1) domain considered to function in transcriptional regulation. In a dual-luciferase assay using Arabidopsis protoplasts, we showed that induction of the TCR1 gene by tunicamycin is independent of a nucleotide sequence similar to the cis-element ER stress response element on its promoter. Our result further indicates that this induction could be mediated by the transcription factor AtbZIP60. This study is a first step to understand the role of TCR1 in the Arabidopsis ER stress response. Key words:Arabidopsis thaliana, CCT domain, endoplasmic reticulum stress, tunicamycin, unfolded protein response.Plant Biotechnology 25, 397-402 (2008) Gene NoteAbbreviations: bZIP, basic leucine zipper; CCT, CONSTANS, CONSTANS-like, TOC1; ER, endoplasmic reticulum; ERSE, ER stress response element; GUS, b-glucuronidase; TCR1, tunicamycin-induced CONSTANS-like-related 1; UPR, unfolded protein response; P-UPRE, plant-UPR element. a Present address: Huck Institutes of the Life Sciences, Pennsylvania State University, 211 Wartik Laboratory, University Park, PA 16802, USA b Present address: Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan This article can be found at http://www.jspcmb.jp/ Arabidopsis ER stress response, we carried out microarray analysis using tunicamycin, an inhibitor of asparagine-linked glycosylation inducing ER stress. We used an oligonucleotide array (Agilent Arabidopsis 2 Oligo Microarray), which contains 60-mer oligonucleotides for each 21,500 gene derived from ATH1 ver. 3 database of The Institute for Genomic Research. For this experiment, Arabidopsis thaliana Col-0 seedlings were grown in one-half strength MS medium supplemented with 1% (w/v) sucrose in a 16 h light and 8 h dark cycle. RNA was isolated from 10-day-old seedlings before or after 5 mg ml Ϫ1 tunicamycin treatment for 5 h using RNeasy Plant Mini Kit (QIAGEN) according to the manufacturer's instructions, and subjected to microarray analysis. The report of the detailed results of the microarray analysis is being preparation for publication (Iwata et al. in preparation).This microarray analysis identified a tunicamycininducible gene encoding a plant-specific CCT (CONSTANS, CONSTANS-like, TOC1) domaincontaining protein, here designated as TCR1 ( Figure 1A). In addition, the GATA-type zincfinger protein expressed in inflorescence meristem, ZIM, and tw...

Alteration of the bZIP60/IRE1 Pathway Affects Plant Response to ER Stress in Arabidopsis thaliana

“…In unstressed seedlings, bZIP60 protein appears in full-length form localized to the ER. Following treatment with stress agents a smaller form of the protein was detected in nuclei [6] . The smaller form of the protein activates the expression of ER stress response genes such as ER-resident chaperone BiP (Binding Protein) [7] .…”

Genome-wide analysis of the CCT gene family in Chinese white pear (Pyrus bretschneideri Rehd.) and characterization of PbPRR2 in response to varying light signals

“…The CCT domain has important functions in nuclear localization, protein–protein interactions, transcriptional regulation and nuclear protein transport [ 3 – 5 ]. CCT family genes can be divided into five categories based on the sequencing information of Arabidopsis : COL, PRR ( P seudo- R esponse R egulator), ZIM ( Z inc-finger Protein Expressed in I nflorescence M eristem), TCR1 ( T unicamycin-induced C OL- R elated 1 ) and ASML2 ( A ctivator of S po m in :: L UC 2 ) subfamilies [ 6 , 7 ]. The CCT family has been comprehensively analysed in some plants, including Arabidopsis , rice, maize, brachypodium, sorghum, foxtail millet, barley, Aegilops tauschii and Medicago truncatula [ 7 – 11 ], but not yet in woody perennial fruit crops.…”

“…ZIM subfamily genes, including ZIM and ZIM-like ( ZML ) genes, are involved in hypocotyls and petiole elongation, cryptochrome 1-dependent responses to excess light and wound-induced lignification [ 33 – 35 ]. TCR1 and ASML2 subfamilies represent two distinct classes of the CCT family, and both encode proteins possessing just a single CCT domain [ 6 , 7 ]. The AtTCR1 gene has been shown to be transcriptionally induced by Arabidopsis endoplasmic reticulum stress [ 7 ].…”

“…TCR1 and ASML2 subfamilies represent two distinct classes of the CCT family, and both encode proteins possessing just a single CCT domain [ 6 , 7 ]. The AtTCR1 gene has been shown to be transcriptionally induced by Arabidopsis endoplasmic reticulum stress [ 7 ]. AtCIA2 , AtCIL , and their barley homologues ( HvCMF3 and HvCMF7 ) belong to the TCR1 subfamily and play critical roles in chloroplast development, thylakoid morphology, photosynthetic activity and various abiotic stress responses [ 36 – 39 ].…”