Determination of the Absolute Configuration of a Monoglyceride Antibolting Compound and Isolation of Related Compounds from Radish Leaves (Raphanus sativus).

A monoglyceride (1) has been reported to possess an antibolting effect in radish (Raphanus sativus), but its absolute configuration at the C-2 position was not determined earlier. In this work, the absolute configuration of 1 was determined to be (2S), and it was also accompanied by one new (2) and two known monoglycerides (3 and 4). The chemical structure of 2 was determined as ß-(7'Z,10'Z,13'Z)-hexadecatrienoic acid monoglyceride (ß-16:3 monoglyceride). Qualitative and quantitative analytical methods for compounds 1-4 were developed, using two deuterium-labeled compounds (8 and 9) as internal standards. The results revealed a broader range of distribution of 1-4 in several annual winter crops. It was also found that these isolated compounds have an inhibitory effect on the root elongation of Arabidopsis thaliana seedlings at concentrations of 25 and 50 µM in the medium. However, the inhibitory effect of 1 was not dependent on coronatin-insensitive 1 (COI1) protein, which may suggest the involvement of an unidentified signaling system other than jasmonic acid signaling.

Elucidation of the biosynthetic pathway of cis-jasmone in Lasiodiplodia theobromae.

In plants, cis-jasmone (CJ) is synthesized from α-linolenic acid (LA) via two biosynthetic pathways using jasmonic acid (JA) and iso-12-oxo-phytodienoic acid (iso-OPDA) as key intermediates. However, there have been no reports documenting CJ production by microorganisms. In the present study, the production of fungal-derived CJ by Lasiodiplodia theobromae was observed for the first time, although this production was not observed for Botrytis cinerea, Verticillium longisporum, Fusarium oxysporum, Gibberella fujikuroi, and Cochliobolus heterostrophus. To investigate the biosynthetic pathway of CJ in L. theobromae, administration experiments using [18,18,18-2H3, 17,17-2H2]LA (LA-d5), [18,18,18-2H3, 17,17-2H2]12-oxo-phytodienoic acid (cis-OPDA-d5), [5',5',5'-2H3, 4',4'-2H2, 3'-2H1]OPC 8:0 (OPC8-d6), [5',5',5'-2H3, 4',4'-2H2, 3'-2H1]OPC 6:0 (OPC6-d6), [5',5',5'-2H3, 4',4'-2H2, 3'-2H1]OPC 4:0 (OPC4-d6), and [11,11-2H2, 10,10-2H2, 8,8-2H2, 2,2-2H2]methyl iso-12-oxo-phytodienoate (iso-MeOPDA-d8) were carried out, revealing that the fungus produced CJ through a single biosynthetic pathway via iso-OPDA. Interestingly, it was suggested that the previously predicted decarboxylation step of 3,7-didehydroJA to afford CJ might not be involved in CJ biosynthesis in L. theobromae.

CYP94B3 activity against jasmonic acid amino acid conjugates and the elucidation of 12-O-ß-glucopyranosyl-jasmonoyl-L-isoleucine as an additional metabolite.

The hormonal action of jasmonate in plants is controlled by the precise balance between its biosynthesis and inactivation. Oxidation of jasmonoyl-L-isoleucine at the C-12 position, which is catalyzed by cytochrome P450s CYP94B3 and CYP94C1, is thought to be one of the main inactivation pathways. In this study, an additional function of CYP94B3 was elucidated, as well additional jasmonoyl-L-isoleucine metabolites being investigated. It was found that CYP94B3 also catalyzes the hydroxylation of jasmonoyl-L-valine and jasmonoyl-L-phenylalanine, and that these hydroxyl compounds accumulated after wounding and possessed lower activity than non-hydroxylated compounds. Additionally, 12-O-ß-glucopyranosyl-jasmonoyl-L-isoleucine accumulated after wounding, suggesting that it is a metabolite of jasmonoyl-L-isoleucine.