Biosynthesis of jasmonic acid in a plant pathogenic fungus, Lasiodiplodia theobromae

Jasmonic acid (JA) is a plant hormone that plays an important role in a wide variety of plant physiological processes. The plant pathogenic fungus, Lasiodiplodia theobromae also produces JA; however, the biosynthesis of JA in this fungus has yet to be explored. A feeding experiment incorporating 13C-labeled sodium acetate.[1-13C] and [2-13C]-into L. theobromae revealed that JA in this fungus originates from a fatty acid synthetic pathway. The methyl ester of 12-oxo-phytodienoic acid (OPDA) was detected in the culture extracts of L. theobromae by GC-MS analysis. This finding indicates the presence of OPDA (a known intermediate of JA biosynthesis in plants) in L. theobromae. 2H-NMR spectral data of JA produced by L. theobromae with the incorporation of [9,10,12,13,15,16-2H6]linolenic acid showed that five deuterium atoms remained intact. In plants, this is speculated to arise from JA being produced by the octadecanoid pathway. However, the observed stereoselectivity of the cyclopentenone olefin reduction in L. theobromae was contrary to that observed in plants. These data suggest that JA biosynthesis in L. theobromae is similar to that in plants, but differing in the facial selectivity of the enone reduction

Effective Synthesis of a Carbon-linked Diazirinyl Fatty Acid Derivative via Reduction of the Carbonyl Group to Methylene with Triethylsilane and Trifluoroacetic Acid

Friedel-Crafts acylation of the aryldiazirine with omega-ester-alpha-acyl halide and successive reduction of the carbonyl group to methylene with triethylsilane and trifluoroacetic acid gave diazirinylated fatty acids

Allene oxide cyclase is essential for theobroxide-induced jasmonic acid biosynthesis in Pharbitis nil

Theobroxide, a natural product, strongly stimulates the biosynthesis of jasmonic acid (JA) in Pharbitis nil. In this study, we investigated the accumulation of protein by the immunoblot analysis of lipoxygenase (LOX), allene oxide synthase (AOS) and allene oxide cyclase (AOC), key enzymes in JA biosynthesis, and how the endogenous levels of JA in Pharbitis nil are affected by theobroxide. The effect of JA on the accumulations of these proteins was monitored simultaneously. The results show that theobroxide treatment led to a high level accumulation of JA, which is due to high accumulations of LOX, AOS and AOC proteins induced by theobroxide treatment both under short day (SD) and long day (LD) conditions. However, under SD conditions AOS and AOC proteins are not enhanced by JA treatment. Kinetic analysis of protein levels show that a biphasic activation of AOC protein by theobroxide is displayed and the first activation of AOC protein together with elevated JA levels are observed within 30 minutes after treatment. Meanwhile, AOS and LOX proteins are activated by theobroxide later than AOC protein, suggesting that AOC plays an essential role in the initial JA formation induced by theobroxide. Since theobroxide-increased JA levels also show a biphasic manner similar to AOC activation and AOS, LOX proteins are activated later than AOC, and thus we propose a positive JA feedback regulation. Interestingly, AOS protein, which is also the enzyme for the biosynthesis of 9,10-ketol-octadecadienoic acid (KODA, a flowering inducing factor), accumulates markedly due to the simultaneous involvement of theobroxide and SD conditions, suggesting that AOS probably plays a role in flower bud formation in Pharbitis nil

Identification of a β-glucosidase hydrolyzing tuberonic acid glucoside in rice (Oryza sativa L.)

Tuberonic acid (TA) and its glucoside (TAG) have been isolated from potato (Solanum tuberosum L) leaflets and shown to exhibit tuber-inducing properties. These compounds were reported to be biosynthesized from jasmonic acid (JA) by hydroxylation and subsequent glycosylation, and to be contained in various plant species. Here we describe the in vivo hydrolytic activity of TAG in rice. In this study, the TA resulting from TAG was not converted into JA. Tuberonic acid glucoside (TAG)-hydrolyzing β-glucosidase, designated OsTAGG1, was purified from rice by six purification steps with an similar to 4300-fold purification. The purified enzyme migrated as a single band on native PAGE, but as two bands with 4300-fold purification. The purified enzyme migrated as a single band on native PAGE, but as two bands with molecular masses of 42 and 26 kDa on SDS-PAGE. The results from N-terminal sequencing and peptide mass fingerprinting of both polypeptides suggested that the two bands were derived from a single polypeptide, which is a member of glycosyl hydrolase family 1. In the native enzyme, the Km and Vmax values of TAG were 31.7 μM and and 14.7 μmol/min/mg, respectively. OsTAGG1 preferentially hydrolyzed TAG and methyl TAG. Here we report that OsTAGG1 is a specific β-glucosidase hydrolyzing TAG, which releases physiologically active TA