The barley magnesium chelatase 150-kd subunit is not an abscisic acid receptor.
Magnesium chelatase is the first unique enzyme of the chlorophyll biosynthetic pathway. It is composed of three gene products of which the largest is 150 kD. This protein was recently identified as an abscisic acid receptor in Arabidopsis (Arabidopsis thaliana). We have evaluated whether the barley (Hordeum vulgare) magnesium chelatase large subunit, XanF, could be a receptor for the phytohormone. The study involved analysis of recombinant magnesium chelatase protein as well as several induced chlorophyll-deficient magnesium chelatase mutants with defects identified at the gene and protein levels. Abscisic acid had no effect on magnesium chelatase activity and binding to the barley 150-kD protein could not be shown. Magnesium chelatase mutants showed a wild-type response in respect to postgermination growth and stomatal aperture. Our results question the function of the large magnesium chelatase subunit as an abscisic acid receptor.
Müller
André H
AH
Carlsberg Laboratory, DK-2500 Valby, Copenhagen, Denmark.
Hansson
Mats
M
D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D000595:Amino Acid Sequence; D018525:Germination; D001467:Hordeum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D008190:Lyases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D054046:Plant Stomata / Q000187:drug effects; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment
D010937:Plant Growth Regulators; D010940:Plant Proteins; D021122:Protein Subunits; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D000040:Abscisic Acid; D008190:Lyases; C086788:magnesium chelatase