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ZmbZIP60 mRNA is spliced in maize in response to ER stress.

Li Y, Humbert S, Howell SH - BMC Res Notes (2012)

Bottom Line: Splicing converts the predicted protein from a membrane-associated transcription factor to one that is targeted to the nucleus.Maize has numerous BIP-like genes, and ER stress was found to upregulate one of these, ZmBIPb.Among the genes upregulated by ER stress in maize is one of 22 BIP-like genes, ZmBIPb.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Sciences Institute, Iowa State University, Ames, IA 50014, USA.

ABSTRACT

Background: Adverse environmental conditions produce ER stress and elicit the unfolded protein response (UPR) in plants. Plants are reported to have two "arms" of the ER stress signaling pathway-one arm involving membrane-bound transcription factors and the other involving a membrane-associated RNA splicing factor, IRE1. IRE1 in yeast to mammals recognizes a conserved twin loop structure in the target RNA.

Results: A segment of the mRNA encoding ZmbZIP60 in maize can be folded into a twin loop structure, and in response to ER stress this mRNA is spliced, excising a 20b intron. Splicing converts the predicted protein from a membrane-associated transcription factor to one that is targeted to the nucleus. Splicing of ZmbZIP60 can be elicited in maize seedlings by ER stress agents such as dithiothreitol (DTT) or tunicamycin (TM) or by heat treatment. Younger, rather than older seedlings display a more robust splicing response as do younger parts of leaf, along a developmental gradient in a leaf. The molecular signature of an ER stress response in plants includes the upregulation of Binding Protein (BIP) genes. Maize has numerous BIP-like genes, and ER stress was found to upregulate one of these, ZmBIPb.

Conclusions: The splicing of ZmbZIP60 mRNA is an indicator of ER stress in maize seedlings resulting from adverse environmental conditions such as heat stress. ZmbZIP60 mRNA splicing in maize leads predictively to the formation of active bZIP transcription factor targeted to the nucleus to upregulate stress response genes. Among the genes upregulated by ER stress in maize is one of 22 BIP-like genes, ZmBIPb.

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IRE1 recognition sites in ZmbZIP60 mRNA and predicted protein. Diagram comparing RNA secondary structure predicted from Mfold for a segment of (A) AtbZIP60 mRNA and (B) ZmbZIP60 mRNA. (C) Partial predicted protein sequence encoded by unspliced ZmbZIP60 mRNA. Splice sites are indicated by arrows and the 20b intron is underlined. The predicted TMD is indicated in italics. (D) Partial predicted protein sequence encoded by spliced ZmbZIP60 mRNA. The arrow indicates the splice junction. The novel sequence produced by the frameshift is indicated in red. The putative nuclear localization signal is underlined. (E) Diagram showing the structures of the predicted proteins encoded by unspliced and spliced ZmbZIP60 mRNAs.
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Figure 1: IRE1 recognition sites in ZmbZIP60 mRNA and predicted protein. Diagram comparing RNA secondary structure predicted from Mfold for a segment of (A) AtbZIP60 mRNA and (B) ZmbZIP60 mRNA. (C) Partial predicted protein sequence encoded by unspliced ZmbZIP60 mRNA. Splice sites are indicated by arrows and the 20b intron is underlined. The predicted TMD is indicated in italics. (D) Partial predicted protein sequence encoded by spliced ZmbZIP60 mRNA. The arrow indicates the splice junction. The novel sequence produced by the frameshift is indicated in red. The putative nuclear localization signal is underlined. (E) Diagram showing the structures of the predicted proteins encoded by unspliced and spliced ZmbZIP60 mRNAs.

Mentions: The consensus substrate recognition sequence for IRE1 is a pair of kissing hairpin loops with three conserved bases in each loop [28]. Both maize and Arabidopsis bZIP60 mRNAs fold into comparable structures (Figure 1A and 1B). All of the bZIP60-related plant genes identified in this study by blast searches have sequences predicted to form IRE1 recognition sites (Additional file 3). In general, the sites in monocots appear to have a shorter interloop bridge sequence than dicots.


ZmbZIP60 mRNA is spliced in maize in response to ER stress.

Li Y, Humbert S, Howell SH - BMC Res Notes (2012)

IRE1 recognition sites in ZmbZIP60 mRNA and predicted protein. Diagram comparing RNA secondary structure predicted from Mfold for a segment of (A) AtbZIP60 mRNA and (B) ZmbZIP60 mRNA. (C) Partial predicted protein sequence encoded by unspliced ZmbZIP60 mRNA. Splice sites are indicated by arrows and the 20b intron is underlined. The predicted TMD is indicated in italics. (D) Partial predicted protein sequence encoded by spliced ZmbZIP60 mRNA. The arrow indicates the splice junction. The novel sequence produced by the frameshift is indicated in red. The putative nuclear localization signal is underlined. (E) Diagram showing the structures of the predicted proteins encoded by unspliced and spliced ZmbZIP60 mRNAs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3369818&req=5

Figure 1: IRE1 recognition sites in ZmbZIP60 mRNA and predicted protein. Diagram comparing RNA secondary structure predicted from Mfold for a segment of (A) AtbZIP60 mRNA and (B) ZmbZIP60 mRNA. (C) Partial predicted protein sequence encoded by unspliced ZmbZIP60 mRNA. Splice sites are indicated by arrows and the 20b intron is underlined. The predicted TMD is indicated in italics. (D) Partial predicted protein sequence encoded by spliced ZmbZIP60 mRNA. The arrow indicates the splice junction. The novel sequence produced by the frameshift is indicated in red. The putative nuclear localization signal is underlined. (E) Diagram showing the structures of the predicted proteins encoded by unspliced and spliced ZmbZIP60 mRNAs.
Mentions: The consensus substrate recognition sequence for IRE1 is a pair of kissing hairpin loops with three conserved bases in each loop [28]. Both maize and Arabidopsis bZIP60 mRNAs fold into comparable structures (Figure 1A and 1B). All of the bZIP60-related plant genes identified in this study by blast searches have sequences predicted to form IRE1 recognition sites (Additional file 3). In general, the sites in monocots appear to have a shorter interloop bridge sequence than dicots.

Bottom Line: Splicing converts the predicted protein from a membrane-associated transcription factor to one that is targeted to the nucleus.Maize has numerous BIP-like genes, and ER stress was found to upregulate one of these, ZmBIPb.Among the genes upregulated by ER stress in maize is one of 22 BIP-like genes, ZmBIPb.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Sciences Institute, Iowa State University, Ames, IA 50014, USA.

ABSTRACT

Background: Adverse environmental conditions produce ER stress and elicit the unfolded protein response (UPR) in plants. Plants are reported to have two "arms" of the ER stress signaling pathway-one arm involving membrane-bound transcription factors and the other involving a membrane-associated RNA splicing factor, IRE1. IRE1 in yeast to mammals recognizes a conserved twin loop structure in the target RNA.

Results: A segment of the mRNA encoding ZmbZIP60 in maize can be folded into a twin loop structure, and in response to ER stress this mRNA is spliced, excising a 20b intron. Splicing converts the predicted protein from a membrane-associated transcription factor to one that is targeted to the nucleus. Splicing of ZmbZIP60 can be elicited in maize seedlings by ER stress agents such as dithiothreitol (DTT) or tunicamycin (TM) or by heat treatment. Younger, rather than older seedlings display a more robust splicing response as do younger parts of leaf, along a developmental gradient in a leaf. The molecular signature of an ER stress response in plants includes the upregulation of Binding Protein (BIP) genes. Maize has numerous BIP-like genes, and ER stress was found to upregulate one of these, ZmBIPb.

Conclusions: The splicing of ZmbZIP60 mRNA is an indicator of ER stress in maize seedlings resulting from adverse environmental conditions such as heat stress. ZmbZIP60 mRNA splicing in maize leads predictively to the formation of active bZIP transcription factor targeted to the nucleus to upregulate stress response genes. Among the genes upregulated by ER stress in maize is one of 22 BIP-like genes, ZmBIPb.

Show MeSH
Related in: MedlinePlus