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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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ZmSNAC1 localizes in nuclear speckles after ABA treatment when co-expressed with ZmOST1.ZmSNAC1-GPF localization is presented in the left, co-expressed with ZmOST1-HA in the middle and co-expressed with ZmOST1 [G40R]-HA in the right. Upper panel shows the localization of ZmSNAC1-GFP at the beginning of the experiment, centre panel the same localization after 30 minutes and the bottom panel represents ZmSNAC1-GFP localization after 30 minutes ABA treatment (10 µM).
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pone-0058105-g006: ZmSNAC1 localizes in nuclear speckles after ABA treatment when co-expressed with ZmOST1.ZmSNAC1-GPF localization is presented in the left, co-expressed with ZmOST1-HA in the middle and co-expressed with ZmOST1 [G40R]-HA in the right. Upper panel shows the localization of ZmSNAC1-GFP at the beginning of the experiment, centre panel the same localization after 30 minutes and the bottom panel represents ZmSNAC1-GFP localization after 30 minutes ABA treatment (10 µM).

Mentions: Since ZmSNAC1 is phosphorylated by ZmOST1 after being activated by ABA, we were interested in determining the effects of this phosphorylation on ZmSNAC1, in particularly during ABA dependent signalling. We transiently co-expressed ZmSNAC1 fused to GFP in maize protoplasts together with ZmOST1 and ZmOST1 [G40R] fused to a HA-epitope and checked for fluorescence under a confocal microscope. Using this approach we were able to detect a change of localization of ZmSNAC1-GFP under ABA treatment when co-expressed with ZmOST1-HA to nuclear speckles that was absent when SNAC1-GFP was over-expressed alone (Figure 6). This formation of nuclear speckles is concomitant with a decrease of overall fluorescence that could have implications on protein stability. Furthermore, when we co-expressed ZmSNAC1 with the inactive ZmOST1 [G40R]-HA this speckled localization did not occur, giving strong indication that what we observed with the wild-type kinase was caused by ZmOST1 activity.


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)

ZmSNAC1 localizes in nuclear speckles after ABA treatment when co-expressed with ZmOST1.ZmSNAC1-GPF localization is presented in the left, co-expressed with ZmOST1-HA in the middle and co-expressed with ZmOST1 [G40R]-HA in the right. Upper panel shows the localization of ZmSNAC1-GFP at the beginning of the experiment, centre panel the same localization after 30 minutes and the bottom panel represents ZmSNAC1-GFP localization after 30 minutes ABA treatment (10 µM).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0058105-g006: ZmSNAC1 localizes in nuclear speckles after ABA treatment when co-expressed with ZmOST1.ZmSNAC1-GPF localization is presented in the left, co-expressed with ZmOST1-HA in the middle and co-expressed with ZmOST1 [G40R]-HA in the right. Upper panel shows the localization of ZmSNAC1-GFP at the beginning of the experiment, centre panel the same localization after 30 minutes and the bottom panel represents ZmSNAC1-GFP localization after 30 minutes ABA treatment (10 µM).
Mentions: Since ZmSNAC1 is phosphorylated by ZmOST1 after being activated by ABA, we were interested in determining the effects of this phosphorylation on ZmSNAC1, in particularly during ABA dependent signalling. We transiently co-expressed ZmSNAC1 fused to GFP in maize protoplasts together with ZmOST1 and ZmOST1 [G40R] fused to a HA-epitope and checked for fluorescence under a confocal microscope. Using this approach we were able to detect a change of localization of ZmSNAC1-GFP under ABA treatment when co-expressed with ZmOST1-HA to nuclear speckles that was absent when SNAC1-GFP was over-expressed alone (Figure 6). This formation of nuclear speckles is concomitant with a decrease of overall fluorescence that could have implications on protein stability. Furthermore, when we co-expressed ZmSNAC1 with the inactive ZmOST1 [G40R]-HA this speckled localization did not occur, giving strong indication that what we observed with the wild-type kinase was caused by ZmOST1 activity.

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