Biosynthesis of Abscisic Acid by the Direct PathwayviaIonylideneethane in a Fungus,Cercospora cruenta

Abstract

We examined the biosynthetic pathway of abscisic acid (ABA) after isopentenyl diphosphate in a fungus, Cercospora cruenta. All oxygen atoms at C-1, -1, -1 0 , and -4 0 of ABA produced by this fungus were labeled with 18 O from 18 O 2 . The fungus did not produce the 9Z-carotenoid possessing -ring that is likely a precursor for the carotenoid pathway, but produced new sesquiterpenoids, 2E,4E--ionylideneethane and 2Z,4E--ionylideneethane, along with 2E,4E,6E-allofarnesene. The fungus converted these sesquiterpenoids labeled with 13 C to ABA, and the incorporation ratio of 2Z,4E--ionylideneethane was higher than that of 2E,4E--ionylideneethane. From these results, we concluded that C. cruenta biosynthesized ABA by the direct pathway via oxidation of ionylideneethane with molecular oxygen following cyclization of allofarnesene. This direct pathway via ionylideneethane in the fungus is consistent with that in Botrytis cinerea, except for the positions of double bonds in the rings of biosynthetic intermediates, suggesting that the pathway is common among ABAproducing fungi.

ABA in bryophytes: how a universal growth regulator in life became a plant hormone?

“…Phytopathogenic fungi such as Botrytis cinerea and Cercospora cruenta are known to release large amounts of ABA (Hirai et al 2000;Inomata et al 2004;Siewers et al 2004;Zhang et al 1999). The fungal ABA biosynthetic pathway has been suggested to be different from that in seed plants.…”

“…The fungal ABA biosynthetic pathway has been suggested to be different from that in seed plants. While plants biosynthesize ABA from farnesyl diphosphate via an indirect pathway (carotenoid pathway), fungal ABA biosynthesis has been proposed to involve direct cyclization of farnesyl diphosphate and subsequent oxidation steps (direct pathway) (Inomata et al 2004;Nambara and Marion-Poll 2005). Recently, genes for the direct pathway have been cloned from B. cinerea (Siewers et al 2004(Siewers et al , 2006.…”

New abscisic acid-related metabolites fromPhellinus vaninii

“…Compound 2 was obtained as a colorless oil with ½a 20 D 2 8.9 (c ¼ 0.23, MeOH). The molecular formula was determined to be C 15 ( 1 H NMR, 13 C NMR, HSQC, HMBC, 1 H-1 H COSY) revealed that compound 2 had a similar basic skeleton as compound 1 ( Table 1). The difference is that the hydroxyl group was at C-3 0 in 1 and at C-4 0 in 2.…”

Biosynthetic considerations could assist the structure elucidation of host plant produced rhizosphere signalling compounds (strigolactones) for arbuscular mycorrhizal fungi and parasitic plants

“…Boud. [3] and (2Z,4E )-g-ionylideneacetaldehyde in Cercospora cruenta [50] which has been reported to be a precursor of abscisic acid biosynthesis in fungi [25]. So far they have not been reported in higher plants, but their occurrence in small amounts can also not be ruled out.…”

“…2. Hydroxylation at the allylic position in 5-deoxystrigol (3) can occur either without e as in the formation of strigol and orobanchol e or with the migration of the double bond leading to different compounds (10) and (25) (Fig. 6).…”