Characterization of the Fungal Gibberellin Desaturase as a 2-Oxoglutarate-Dependent Dioxygenase and Its Utilization for Enhancing Plant Growth    

Abstract

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-oxoglutaratedependent 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.

Gibberellins and the Red Pigments Bikaverin and Fusarubin

“…When fi rst described in 2003, only one potential homologue had been found by BLAST search with very low sequence similarity, a 7α(alpha)-cephem-methoxylase from Nocardia lactamdurans [ 121 ]. Only recently it has been shown by heterologous gene expression in Escherichia coli that Des has the characteristics of a 2-oxoglutarate-dependent dioxygenase, however with very low amino acid sequence similarity with known 2-oxoglutarate-dependent dioxygenases [ 124 ]. Expression of the fungal DES gene from the caulifl ower mosaic virus 35S promoter in the plant species Solanum nigrum , S. dulcamara , and Nicotiana sylvestris resulted in substantial growth stimulation, with a threefold increase in height compared with controls.…”

Cassava Superelongation Disease in the Caribbean

“…In standard incubations it was determined that the wildtype strain of S. manihoticola (DSM1638 from the Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures) produced GA 4 in concentrations of up to 7 mg per liter of culture filtrate. Sphaceloma manihoticola does not produce the commercial gibberellins of GA 3 , GA 1 or GA 7 which are also synthesized by F. fujikuroi, thus with GA 4 being the main gibberellin produced by S. manihoticola it can be isolated in a pure form from culture filtrates of the pathogen [26,27,35].…”

Molecular genetic and biochemical analysis of gibberellic acid involvement in the stages of soybean (Glycine max L.) nodule development

“…GA12 is converted to GA14 by GA3ox, then into GA4 by GA20ox Tudzynski et al, 2002). Recently, GA4-desaturase was shown to be a 2ODDs; it is responsible for deactivation of GA4 into GA7 (Bhattacharya et al, 2012). GA7 is then converted into GA3 by a GA13ox, another P450 Tudzynski et al, 2003).…”

“…Plants required that GA biosynthesis is tightly regulated as the optimum level of GA present in a given tissue is vital to normal growth and development (Bhattacharya et al, 2012). In contrast, as fungi mostly use GA to manipulate plant behaviour, their biosynthetic pathway does not seem to possess such tight regulation (Bhattacharya et al, 2012).…”

“…In contrast, as fungi mostly use GA to manipulate plant behaviour, their biosynthetic pathway does not seem to possess such tight regulation (Bhattacharya et al, 2012).…”