title: The dynamic of the splicing of bZIP60 and the proteins encoded by the spliced and unspliced mRNAs reveals some unique features during the activation of UPR in Arabidopsis thaliana.
abstract: The unfolded protein response (UPR) is a signaling pathway that is activated when the workload of the endoplasmic reticulum (ER) is surpassed. IRE1 is a sensor involved in triggering the UPR and plays a key role in the unconventional splicing of an mRNA leading to the formation of a transcription factor that up-regulates the transcription of genes that play a role in restoring the homeostasis in the ER. In plants, bZIP60 is the substrate for IRE1; however, questions such as what is the dynamics of the splicing of bZIP60 and the fate of the proteins encoded by the spliced and unspliced forms of the mRNA, remain unanswered. In the present work, we analyzed the processing of bZIP60 by determining the levels of the spliced form mRNA in plants exposed to different conditions that trigger UPR. The results show that induction of ER stress increases the content of the spliced form of bZIP60 (bZIP60s) reaching a maximum, that depending on the stimuli, varied between 30 min or 2 hrs. In most cases, this was followed by a decrease in the content. In contrast to other eukaryotes, the splicing never occurred to full extent. The content of bZIP60s changed among different organs upon induction of the UPR suggesting that splicing is regulated differentially throughout the plant. In addition, we analyzed the distribution of a GFP-tagged version of bZIP60 when UPR was activated. A good correlation between splicing of bZIP60 and localization of the protein in the nucleus was observed. No fluorescence was observed under basal conditions, but interestingly, the fluorescence was recovered and found to co-localize with an ER marker upon treatment with an inhibitor of the proteasome. Our results indicate that the dynamics of bZIP60, both the mRNA and the protein, are highly dynamic processes which are tissue-specific and stimulus-dependent.
authors: Centro de Biotecnología Vegetal, FONDAP Center for Genome Regulation, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors: Juan
authors: J
authors: Parra-Rojas
authors: Centro de Biotecnología Vegetal, FONDAP Center for Genome Regulation, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors: Adrian A
authors: AA
authors: Moreno
authors: Centro de Biotecnología Vegetal, FONDAP Center for Genome Regulation, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors: Irina
authors: I
authors: Mitina
authors: Centro de Biotecnología Vegetal, FONDAP Center for Genome Regulation, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors: Ariel
authors: A
authors: Orellana
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D019075:Electrophoresis, Capillary; D004721:Endoplasmic Reticulum / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000378:metabolism; D008353:Mannitol / Q000494:pharmacology; D018613:Microscopy, Confocal; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012326:RNA Splicing / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020156:Salicylic Acid / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013696:Temperature; D015533:Transcriptional Activation; D014415:Tunicamycin / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D012333:RNA, Messenger; C533092:bZIP60 protein, Arabidopsis; D014415:Tunicamycin; D008353:Mannitol; D012965:Sodium Chloride; D046988:Proteasome Endopeptidase Complex; D020156:Salicylic Acid; D004229:Dithiothreitol