Identification of an Arabidopsis transmembrane bZIP transcription factor involved in the endoplasmic reticulum stress response

Tajima, Hiromi; Iwata, Yuji; Iwano, Megumi; Takayama, Seiji; Koizumi, Nozomu

doi:10.1016/j.bbrc.2008.07.021

Cited by 119 publications

(142 citation statements)

References 35 publications

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“…ER stress was induced in wild-type and AtBAG7-knockout mutants by heat treatment (50°C for 30 min) or cold treatment (−20°C for 90 min), and the expression patterns of AtBAG7 and the ER stress markers BiP1/BiP2, BiP3, CNX, CRT, protein disulfide isomerase, and Bax inhibitor (Bi-1) were quantified by real-time PCR (Table S1) . Consistent with previous studies, the real-time data demonstrated increases in chaperone expression for both heat and cold treatment in wild-type plants (22,30,31,36). The real-time analysis failed to demonstrate an increase in AtBAG7 transcript for either heat or cold treatment.…”

Section: During Abiotic Stress Bip3 Transcript Levels Are Increased Isupporting

confidence: 78%

“…Although the demonstration of AtBAG7 and BiP interaction via BiFC assays suggests a role for AtBAG7 as a cochaperone for the maintenance of the UPR, further studies were required to confirm this interaction. Tm, a specific inducer of ER stress, has been used to identify key regulators of ER stress pathways including BiP, Bi-1, and the membrane-tethered transcription factors bZIP28 and bZIP60 (22,28,30,31,36). Consistent with these studies, AtBAG7 knockouts were significantly more sensitive than wild-type plants to Tm treatment.…”

Section: Discussionsupporting

confidence: 66%

“…The previous results demonstrate a chaperoning activity for AtBAG7 during stress and maintenance of the UPR. Numerous studies have shown increased levels of ER chaperones, including BiP and Ca 2+ -dependent ER folding proteins, during ER stress and the UPR, (22,30,31,36). Therefore, using real-time PCR, we considered whether AtBAG7 expression also is induced upon ER stress.…”

Section: During Abiotic Stress Bip3 Transcript Levels Are Increased Imentioning

confidence: 99%

“…During ER stress, BiP and other Ca 2 + -dependent folding proteins, including calreticulin (CRT) and calnexin (CNX), are expressed as part of the UPR to create an optimal environment for proper protein folding (17,19,21,(27)(28)(29)(30)(31). Because AtBAG7 interacts with a major mediator of ER stress, AtBiP, we considered whether it plays a role within the UPR.…”

Section: Atbag7 Is Involved In Maintenance Of the Unfolded Protein Rementioning

confidence: 99%

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AtBAG7 , an Arabidopsis Bcl-2–associated athanogene, resides in the endoplasmic reticulum and is involved in the unfolded protein response

Williams

Kabbage

Britt

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

127

155

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The Bcl-2-associated athanogene (BAG) family is an evolutionarily conserved, multifunctional group of cochaperones that perform diverse cellular functions ranging from proliferation to growth arrest and cell death in yeast, in mammals, and, as recently observed, in plants. The Arabidopsis genome contains seven homologs of the BAG family, including four with domain organization similar to animal BAGs. In the present study we show that an Arabidopsis BAG, AtBAG7, is a uniquely localized endoplasmic reticulum (ER) BAG that is necessary for the proper maintenance of the unfolded protein response (UPR). AtBAG7 was shown to interact directly in vivo with the molecular chaperone, AtBiP2, by bimolecular fluorescence complementation assays, and the interaction was confirmed by yeast two-hybrid assay. Treatment with an inducer of UPR, tunicamycin, resulted in accelerated cell death of AtBAG7-null mutants. Furthermore, AtBAG7 knockouts were sensitive to known ER stress stimuli, heat and cold. In these knockouts heat sensitivity was reverted successfully to the wild-type phenotype with the addition of the chemical chaperone, tauroursodexycholic acid (TUDCA). Real-time PCR of ER stress proteins indicated that the expression of the heat-shock protein, AtBiP3, is selectively up-regulated in AtBAG7-null mutants upon heat and cold stress. Our results reveal an unexpected diversity of the plant's BAG gene family and suggest that AtBAG7 is an essential component of the UPR during heat and cold tolerance, thus confirming the cytoprotective role of plant BAGs.programmed cell death | chaperones | cytoprotection

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Section: During Abiotic Stress Bip3 Transcript Levels Are Increased Isupporting

confidence: 78%

Section: Discussionsupporting

confidence: 66%

Section: During Abiotic Stress Bip3 Transcript Levels Are Increased Imentioning

confidence: 99%

Section: Atbag7 Is Involved In Maintenance Of the Unfolded Protein Rementioning

confidence: 99%

See 2 more Smart Citations

AtBAG7 , an Arabidopsis Bcl-2–associated athanogene, resides in the endoplasmic reticulum and is involved in the unfolded protein response

Williams

Kabbage

Britt

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

127

155

View full text Add to dashboard Cite

show abstract

“…This protein also shares the S1P and S2P cleavage sites present in ATF6 from mammals, but only the effect of the S2P serine protease in releasing the active form of bZIP28 has been studied (Che et al, 2010). The transcription factor activity of bZIP28 has been demonstrated using promoters of ER chaperone genes such as BiP and BiP3 and a construction harboring hexamer of the ERSE and P-UPRE elements fused to the 35S minimal promoter in transactivation assays (Tajima et al, 2008). In addition, Liu et al (2007b) proved that plants overexpressing the active form of bZIP28 (which lacks the transmembrane domain located in the C-terminal part of the protein) have an enhanced expression of ER chaperone genes, such as BiP, BiP3, PDIL, CRT1 and CNX1.…”

Section: The Upr Signaling Mechanism In Plantsmentioning

confidence: 99%

The physiological role of the unfolded protein response in plants

Moreno

Orellana

2011

Biol. Res.

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SUMMARYUnfolded protein response (UPR) is a signaling mechanism activated by misfolded protein accumulation in the endoplasmic reticulum. It is a widespread process that has been described in organisms ranging from yeasts to mammals. In recent years, our understanding of UPR signaling pathway in plants has advanced. Two transcription factors from Arabidopsis thaliana have been reported to function as the sensor/ transducer of this response (AtbZIP60 and AtbZIP28). They seem to be involved in both heat and biotic stress. Furthermore, overexpression of one of them (AtbZIP60) produces plants with a higher tolerance for salt stress, suggesting that this transcription factor may play a role in abiotic stress. Furthermore, some data suggest that crosstalk between genes involved in abiotic stress and UPR may also exist in plants. On the other hand, UPR is related to programmed cell death (PCD) in plants given that that triggering UPR results in induction of PCD-related genes. This article reviews the latest progress in understanding UPR signaling in plants and analyzes its relationship to key processes in plant physiology.

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The endoplasmic reticulum stress signaling pathways in plants

Urade

2009

BioFactors

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The unfolded protein response (UPR) is an evolutionarily conserved mechanism by which all eukaryotic cells preserve the homeostasis of the endoplasmic reticulum (ER) in the face of accumulation of unfolded proteins in the ER. Plants possess at least two signaling pathways specific for UPR. ER membrane-bound ER stress sensor/transducers, AtbZIP60 and AtbZIP28, are basic leucine zipper transcription factors that are activated by regulated intramembrane proteolysis systems and regulate transcription of the UPR genes. These signaling pathways play important roles not only in the UPR but also in other biological processes such as the response to pathogens and heat stress.

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Identification of an Arabidopsis transmembrane bZIP transcription factor involved in the endoplasmic reticulum stress response

Cited by 119 publications

References 35 publications

AtBAG7 , an Arabidopsis Bcl-2–associated athanogene, resides in the endoplasmic reticulum and is involved in the unfolded protein response

AtBAG7 , an Arabidopsis Bcl-2–associated athanogene, resides in the endoplasmic reticulum and is involved in the unfolded protein response

The physiological role of the unfolded protein response in plants

The endoplasmic reticulum stress signaling pathways in plants

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