An allene oxide and 12-oxophytodienoic acid are key intermediates in jasmonic acid biosynthesis by Fusarium oxysporum

Abstract

Fungi can produce jasmonic acid (JA) and its isoleucine conjugate in large quantities, but little is known about the biosynthesis. Plants form JA from 18:3-3 by 13-lipoxygenase (LOX), allene oxide synthase, and allene oxide cyclase. Shaking cultures of f. sp. released over 200 mg of jasmonates per liter. Nitrogen powder of the mycelia expressed 10-dioxygenase-epoxy alcohol synthase activities, which was confirmed by comparison with the recombinant enzyme. The 13-LOX of could not be detected in the cell-free preparations. Incubation of mycelia in phosphate buffer with [17,17,18,18,18-H]18:3-3 led to biosynthesis of a [H]12-oxo-13-hydroxy-9,15-octadecadienoic acid (α-ketol), [H]12-oxo-10,15-phytodienoic acid (12-OPDA), and [H]13-keto- and [H]13-hydroxyoctadecatrienoic acids. The α-ketol consisted of 90% of the 13 stereoisomer, suggesting its formation by nonenzymatic hydrolysis of an allene oxide with 13 configuration. Labeled and unlabeled 12-OPDA were observed following incubation with 0.1 mM [H]18:3-3 in a ratio from 0.4:1 up to 47:1 by mycelia of liquid cultures of different ages, whereas 10 times higher concentration of [H]13-hydroperoxyoctadecatrienoic acid was required to detect biosynthesis of [H]12-OPDA. The allene oxide is likely formed by a cytochrome P450 or catalase-related hydroperoxidase. We conclude that , like plants, forms jasmonates with an allene oxide and 12-OPDA as intermediates.

Biosynthesis of Jasmonates from Linoleic Acid by the Fungus Fusarium oxysporum. Evidence for a Novel Allene Oxide Cyclase

“…Previous work has shown that JA biosynthesis of F. oxysporum is influenced by the growth conditions (Cole et al, ; Oliw and Hamberg, ). Comparison of the expression of CYP mRNA of F. oxysporum under growth in Czapec‐DOX broth under light (with low JA‐Ile biosynthesis) with the expression in PDB in the dark (with high biosynthesis) might indicate potential 13 S ‐AOS candidates (Oliw and Hamberg, ). Whether expressed sequence tags of mRNA could provide this information might be worth further investigations.…”

“…Fig. b) (Oliw and Hamberg, ). This observation lends further support for a tightly controlled process from 18:2n‐6 and 18:3n‐3 to the jasmonate end products.…”

“…This complex accepts exogenous 18:3n‐3 and 18:2n‐6 as substrates and converts them via 12‐OPDA and 12‐OPEA in a tightly controlled process to JA‐Ile and 9,10‐dihydro‐JA‐Ile, respectively. This occurs without significant accumulation of hydroperoxides or α‐ketols in either the growth medium (Miersch et al, , ; Oliw and Hamberg, ; Tsukada et al, ) or in cell‐free preparations. In contrast, added 13 S ‐HPODE and 13 S ‐HPOTrE are readily transformed into allene oxides, but not to cyclopentenone fatty acids (cf.…”

“…13 S ‐HPODE was from Larodan, but also prepared from 18:2n‐6 and [ 13 C 18 ]18:2n‐6 with soybean LOX‐1 (Lipoxidase, Sigma‐Aldrich). 13 S ‐HPOTrE, [17,17,18,18,18‐ 2 H 5 ]‐13 S ‐HPOTrE (d 5 ‐13 S ‐HPOTrE), 13 R ‐HPOTrE and 9( S ) ‐ hydroperoxy ‐ 10( E ),12( Z )‐octadecadienoic acid (9 S ‐HPODE), and 15 S ‐hydroperoxides of 20:2n‐6, 20:3n‐3 and 20:4n‐6 and 11S‐hydroperoxide of 16:3n‐3 were prepared as described (Chen et al, ; Oliw and Hamberg, ). (−)‐JA, isoleucine, and potato dextrose broth (PDB) were from Sigma‐Aldrich.…”

Biosynthesis of Oxylipins by Rhizoctonia solani with Allene Oxide and Oleate 8S,9S‐Diol Synthase Activities

“…Allene oxides can be formed in plants and fungi from 9‐ and 13‐hydroperoxy metabolites of 18:2 n ‐6 and 18:3 n ‐3 (Hamberg, ; Oliw & Hamberg, ; Vick & Zimmerman, ). Of particular biological significance is the biosynthesis of jasmonic acid.…”