ISSN:
1432-072X
Keywords:
Ethylene
;
Ethylene-forming enzyme
;
Fusarium oxysporum
;
Penicillium digitatum
;
2-Oxoglutarate
;
Dioxygenase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Liquid cultures of the deuteromycete, Fusarium oxysporum f. sp. tulipae, a tulip pathogen, produced high amounts of ethylene during stationary phase. 1-Aminocyclopropane-1-carboxylic acid, the direct precursor of ethylene in plants, was not present in the fungus. Radioactivity from [3,4-3H]glutamate as well as [U-14C]glutamate was incorporated into ethylene, indicating that it was derived from C3 and C4 of glutamate or 2-oxoglutarate. Ferrous ions markedly stimulated the rate of ethylene formation in vivo, whereas Fe3+, Cu2+ or Zn2+ had little or no effect. Ethylene biosynthesis was strongly inhibited by the heavy metal chelator α,α′-dipyridine. The effect of α,α′-dipyridine was fully reversed by Fe2+ ions and partially by Cu2+ and Zn2+ ions but not by the supply of glutamate or 2-oxoglutarate, suggesting that a step in the ethylene biosynthetic pathway downstream of 2-oxoglutarate is dependent on Fe2+. When stationary phase cultures were supplied with arginine, ornithine, or proline, ethylene production increased dramatically while addition of glutamate or 2-oxoglutarate had little effect. Tracer studies were performed to test the possibility that an intermediate in the catabolism of arginine to glutamate was the direct precursor of ethylene. In cultures supplied with [U-14C]arginine or [U-14C]glutamate, the specific radioactivity of ethylene was closely similar to the specific radioactivity of the endogenous glutamate pool, indicating that glutamate was on the pathway between arginine and ethylene. An enzyme system converting 2-oxoglutarate to ethylene in a reaction dependent on oxygen, ferrous ions and arginine has previously been described in extracts from Penicillium digitatum (Fukuda et al. 1986). The present results suggest that a similar enzyme system catalyzes the final step of ethylene biosynthesis in F. oxysporum.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00245329
Permalink
