Characterization of the fungal gibberellin desaturase as a 2-oxoglutarate-dependent dioxygenase and its utilization for enhancing plant growth.
The biosynthesis of gibberellic acid (GA(3)) by the fungus Fusarium fujikuroi is catalyzed by seven enzymes encoded in a gene cluster. While four of these enzymes are characterized as cytochrome P450 monooxygenases, the nature of a fifth oxidase, GA(4) desaturase (DES), is unknown. DES converts GA(4) to GA(7) by the formation of a carbon-1,2 double bond in the penultimate step of the pathway. Here, we show by expression of the des complementary DNA in Escherichia coli that DES has the characteristics of a 2-oxoglutarate-dependent dioxygenase. Although it has low amino acid sequence homology with known 2-oxoglutarate-dependent dioxygenases, putative iron- and 2-oxoglutarate-binding residues, typical of such enzymes, are apparent in its primary sequence. A survey of sequence databases revealed that homologs of DES are widespread in the ascomycetes, although in most cases the homologs must participate in non-gibberellin (GA) pathways. Expression of des from the cauliflower mosaic virus 35S promoter in the plant species Solanum nigrum, Solanum dulcamara, and Nicotiana sylvestris resulted in substantial growth stimulation, with a 3-fold increase in height in S. dulcamara compared with controls. In S. nigrum, the height increase was accompanied by a 20-fold higher concentration of GA(3) in the growing shoots than in controls, although GA(1) content was reduced. Expression of des was also shown to partially restore growth in plants dwarfed by ectopic expression of a GA 2-oxidase (GA-deactivating) gene, consistent with GA(3) being protected from 2-oxidation. Thus, des has the potential to enable substantial growth increases, with practical implications, for example, in biomass production.
Plant and Crop Sciences Division, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, United Kingdom.
Anjanabha
A
Bhattacharya
Sofia
S
Kourmpetli
Dennis A
DA
Ward
Stephen G
SG
Thomas
Fan
F
Gong
Stephen J
SJ
Powers
Esther
E
Carrera
Benjamin
B
Taylor
Francisco Nuñez
FN
de Caceres Gonzalez
Bettina
B
Tudzynski
Andrew L
AL
Phillips
Michael R
MR
Davey
Peter
P
Hedden
D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000378:metabolism; D017796:Caulimovirus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D030541:Databases, Genetic; D057075:Enzyme Assays / Q000379:methods; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D005670:Fusarium / Q000201:enzymology* / Q000235:genetics; D005822:Genetic Vectors; D005875:Gibberellins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D032322:Solanum / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D013379:Substrate Specificity; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
D018076:DNA, Complementary; D005656:Fungal Proteins; D005875:Gibberellins; D007656:Ketoglutaric Acids; C007842:gibberellic acid; D006899:Mixed Function Oxygenases