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GrainGenes Reference Report: PLC-13-667

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Reference	PLC-13-667
Title	Gibberellin/abscisic acid antagonism in barley aleurone cells: Site of action of the protein kinase PKABA1 in relation to gibberellin signaling molecules
Journal	Plant Cell
Year	2001
Volume	13
Pages	667-679
Author	Gomez-Cadenas A Zentella R Walker-Simmons MK Ho THD
Abstract	Summary: The antagonism between gibberellins (GA) and abscisic acid (ABA) is an important factor regulating the developmental transition from embryogenesis to seed germination. In barley aleurone layers, the expression of genes encoding alpha-amylases and proteases is induced by GA but suppressed by ABA. It has been shown that an ABA-induced protein kinase, PKABA1, mediates the ABA suppression of alpha-amylase expression. Using a barley aleurone transient expression system, we have now localized the site of action of PKABA1 relative to other signal transduction components governing the expression of alpha-amylase. The expression of alpha-amylase can be transactivated by the transcription factor GAMyb, which is itself induced by GA. A truncated GAMyb containing the DNA binding domain but lacking the transactivation domain prevents the GA induction of alpha-amylase, further supporting the notion that GAMyb mediates the GA induction of alpha-amylase expression. Although ABA and PKABA1 strongly inhibit the GA induction of alpha-amylase, they have no effect on GAMyb-transactivated alpha-amylase expression. Using a GAMyb promoter-beta-glucuronidase construct, we also show that both ABA and PKABA1 repress the GA induction of GAMyb. In the slender mutant, GAMyb and alpha-amylase are highly expressed, even in the absence of GA. However, this constitutive expression can still be inhibited by ABA, PKABA1, or an inhibitor of cGMP synthesis. On the basis of these observations, we suggest that PKABA1 acts upstream from the formation of functional GAMyb but downstream from the site of action of the Slender gene product. Because PKABA1 inhibits the GA induction of the GAMyb promoter-beta-glucuronidase construct, it appears that at least part of the action of PKABA1 is to downregulate GAMyb at the transcriptional level
External Databases	Pubmed: 11251104
Keyword	[ Hide all but 1 of 56 ] aba abscisic acid aleurone aleurone cells aleurone layer alpha alpha amylase alpha amylase gene amylase antagonism barley barley aleurone barley aleurone cells barley aleurone layers binding domain cell cereal aleurone constitutive expression dna dna binding domain embryogenesis gamyb gene gene product germination gibberellin gibberellins hordeum vulgare hormonal regulation induction inhibitor kinase layers messenger rna molecule molecules mutant plasma membrane protease proteases protein kinase response complex seed seed germination signal signal transduction suppression synthesis transactivation transcription transcription factor transduction transient expression transient expression system transition

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