A Mak-like kinase is a repressor of GAMYB in barley aleurone.
GAMYB is a gibberellin (GA)-regulated activator of hydrolase gene expression in the aleurone layer of germinating cereal grains. Although it is clear that GAMYB expression is regulated by GA, more remains to be understood about how this transcription factor operates within the GA-response pathway. In order to isolate new components from the GA-response pathway, barley aleurone libraries were screened for GAMYB-binding proteins using a recently developed yeast two-hybrid system, which is compatible with the use of transcription factors as baits. We isolated a new member of the emerging Mak-subgroup of cdc2- and MAP kinase-related protein kinases. We have termed this GAMYB-binding protein KGM (for kinase associated with GAMYB). Transient expression of KGM specifically repressed alpha-amylase promoter activity at the level of GAMYB function but a mutation designed to de-stabilise the activation loop of KGM alleviated this repression. We propose that KGM is a negative regulator of GAMYB function in aleurone that may prevent precocious hydrolase gene expression.
Woodger
Fiona J
FJ
CSIRO Plant Industry, GPO Box 1600, Canberra, ACT, 2601, Australia. woodger@rsbs.anu.edu.au
Gubler
Frank
F
Pogson
Barry J
BJ
Jacobsen
John V
JV
D000595:Amino Acid Sequence; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018525:Germination / Q000235:genetics / Q000502:physiology; D005875:Gibberellins / Q000494:pharmacology*; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism*; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012639:Seeds / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D020798:Two-Hybrid System Techniques; D000516:alpha-Amylases / Q000378:metabolism
D005875:Gibberellins; D010940:Plant Proteins; D020598:Proto-Oncogene Proteins c-myb; D012097:Repressor Proteins; D020928:Mitogen-Activated Protein Kinases; D000516:alpha-Amylases