MAX3/CCD7 is a carotenoid cleavage dioxygenase required for the synthesis of a novel plant signaling molecule.
BACKGROUND
Plant development is exquisitely environmentally sensitive, with plant hormones acting as long-range signals that integrate developmental, genetic, and environmental inputs to regulate development. A good example of this is in the control of shoot branching, where wide variation in plant form can be generated in a single genotype in response to environmental and developmental cues.


RESULTS
Here we present evidence for a novel plant signaling molecule involved in the regulation of shoot branching. We show that the MAX3 gene of Arabidopsis is required for the production of a graft-transmissible, highly active branch inhibitor that is distinct from any of the previously characterized branch-inhibiting hormones. Consistent with its proposed function in the synthesis of a novel signaling molecule, we show that MAX3 encodes a plastidic dioxygenase that can cleave multiple carotenoids.


CONCLUSIONS
We conclude that MAX3 is required for the synthesis of a novel carotenoid-derived long-range signal that regulates shoot branching.
Department of Biology, University of York, PO Box 373, York YO10 5DD, United Kingdom.
Jonathan
J
Booker
Michele
M
Auldridge
Sarah
S
Wills
Donald
D
McCarty
Harry
H
Klee
Ottoline
O
Leyser
D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000502:physiology*
D029681:Arabidopsis Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D007210:Indoleacetic Acids; D002338:Carotenoids; D000040:Abscisic Acid