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The maize OST1 kinase homolog phosphorylates and regulates the maize SNAC1-type transcription factor.

Vilela B, Moreno-Cortés A, Rabissi A, Leung J, Pagès M, Lumbreras V - PLoS ONE (2013)

Bottom Line: Furthermore, we have identified the transcription factor, ZmSNAC1, which is directly phosphorylated by ZmOST1 with implications on its localization and protein stability.Interestingly, ZmSNAC1 binds to the ABA-box of ZmOST1, which is conserved in SnRK2s activated by ABA and is part of the contact site for the negative-regulating clade A PP2C phosphatases.Taken together, our results indicate that ZmSNAC1 is a substrate of ZmOST1 and delineate a novel osmotic stress transcriptional pathway in maize.

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Agricultural Genomics, Bellaterra, Cerdanyola del Vallés, Spain.

ABSTRACT
The Arabidopsis kinase OPEN STOMATA 1 (OST1) plays a key role in regulating drought stress signalling, particularly stomatal closure. We have identified and investigated the functions of the OST1 ortholog in Z. mays (ZmOST1). Ectopic expression of ZmOST1 in the Arabidopsis ost1 mutant restores the stomatal closure phenotype in response to drought. Furthermore, we have identified the transcription factor, ZmSNAC1, which is directly phosphorylated by ZmOST1 with implications on its localization and protein stability. Interestingly, ZmSNAC1 binds to the ABA-box of ZmOST1, which is conserved in SnRK2s activated by ABA and is part of the contact site for the negative-regulating clade A PP2C phosphatases. Taken together, our results indicate that ZmSNAC1 is a substrate of ZmOST1 and delineate a novel osmotic stress transcriptional pathway in maize.

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ZmOST1 and ZmSNAC1 co-localize in the nucleus.GFP, ZmOST1-GFP, ZmOST1 [G40R]-GFP and ZmSNAC1-GFP fusion proteins were localized by transient expression in epidermal tobacco leaves. Left, GFP signal; right, light microscope/GFP channel overlay.
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pone-0058105-g003: ZmOST1 and ZmSNAC1 co-localize in the nucleus.GFP, ZmOST1-GFP, ZmOST1 [G40R]-GFP and ZmSNAC1-GFP fusion proteins were localized by transient expression in epidermal tobacco leaves. Left, GFP signal; right, light microscope/GFP channel overlay.

Mentions: We monitored the subcellular localization of ZmOST1-GFP and ZmSNAC1-GFP constructs in Nicotiana benthamiana and found that both proteins are localized in the nucleus and the cytoplasm of tobacco epidermal cells (Figure 3). Clade A PP2C phosphatases are upstream negative regulators of OST1 that constitutively inhibit its activity in the absence of ABA. In Arabidopsis, the mutated PP2C, abi1-1, has been shown to require nuclear localization to block stomatal closure [43]. We thus tested whether the subcellular localization of an inactive ZmOST1 kinase (Figure S3) with the point mutation G40R might be altered. This mutated form, however, maintains the same subcellular localization of the wild-type kinase. Unexpectedly, while the level of the wild-type ZmOST1-GFP is low, this mutated form accumulates to higher levels in transformed tobacco cells. Since there is no noticeable altered subcellular localization between the wild-type and the mutant ZmOST1, which is stable, this could explain why the kinases OST1-2 and AAPK similarly mutated in the P-loop could prevent full phenotypic complementation by their respective wild-type counter parts.


The maize OST1 kinase homolog phosphorylates and regulates the maize SNAC1-type transcription factor.

Vilela B, Moreno-Cortés A, Rabissi A, Leung J, Pagès M, Lumbreras V - PLoS ONE (2013)

ZmOST1 and ZmSNAC1 co-localize in the nucleus.GFP, ZmOST1-GFP, ZmOST1 [G40R]-GFP and ZmSNAC1-GFP fusion proteins were localized by transient expression in epidermal tobacco leaves. Left, GFP signal; right, light microscope/GFP channel overlay.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585266&req=5

pone-0058105-g003: ZmOST1 and ZmSNAC1 co-localize in the nucleus.GFP, ZmOST1-GFP, ZmOST1 [G40R]-GFP and ZmSNAC1-GFP fusion proteins were localized by transient expression in epidermal tobacco leaves. Left, GFP signal; right, light microscope/GFP channel overlay.
Mentions: We monitored the subcellular localization of ZmOST1-GFP and ZmSNAC1-GFP constructs in Nicotiana benthamiana and found that both proteins are localized in the nucleus and the cytoplasm of tobacco epidermal cells (Figure 3). Clade A PP2C phosphatases are upstream negative regulators of OST1 that constitutively inhibit its activity in the absence of ABA. In Arabidopsis, the mutated PP2C, abi1-1, has been shown to require nuclear localization to block stomatal closure [43]. We thus tested whether the subcellular localization of an inactive ZmOST1 kinase (Figure S3) with the point mutation G40R might be altered. This mutated form, however, maintains the same subcellular localization of the wild-type kinase. Unexpectedly, while the level of the wild-type ZmOST1-GFP is low, this mutated form accumulates to higher levels in transformed tobacco cells. Since there is no noticeable altered subcellular localization between the wild-type and the mutant ZmOST1, which is stable, this could explain why the kinases OST1-2 and AAPK similarly mutated in the P-loop could prevent full phenotypic complementation by their respective wild-type counter parts.

Bottom Line: Furthermore, we have identified the transcription factor, ZmSNAC1, which is directly phosphorylated by ZmOST1 with implications on its localization and protein stability.Interestingly, ZmSNAC1 binds to the ABA-box of ZmOST1, which is conserved in SnRK2s activated by ABA and is part of the contact site for the negative-regulating clade A PP2C phosphatases.Taken together, our results indicate that ZmSNAC1 is a substrate of ZmOST1 and delineate a novel osmotic stress transcriptional pathway in maize.

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Agricultural Genomics, Bellaterra, Cerdanyola del Vallés, Spain.

ABSTRACT
The Arabidopsis kinase OPEN STOMATA 1 (OST1) plays a key role in regulating drought stress signalling, particularly stomatal closure. We have identified and investigated the functions of the OST1 ortholog in Z. mays (ZmOST1). Ectopic expression of ZmOST1 in the Arabidopsis ost1 mutant restores the stomatal closure phenotype in response to drought. Furthermore, we have identified the transcription factor, ZmSNAC1, which is directly phosphorylated by ZmOST1 with implications on its localization and protein stability. Interestingly, ZmSNAC1 binds to the ABA-box of ZmOST1, which is conserved in SnRK2s activated by ABA and is part of the contact site for the negative-regulating clade A PP2C phosphatases. Taken together, our results indicate that ZmSNAC1 is a substrate of ZmOST1 and delineate a novel osmotic stress transcriptional pathway in maize.

Show MeSH
Related in: MedlinePlus