12-Hydroxyjasmonate, also known as tuberonic acid, was first isolated from Solanum tuberosum and was shown to have tuber-inducing properties. It is derived from the ubiquitously occurring jasmonic acid, an important signaling molecule mediating diverse developmental processes and plant defense responses. We report here that the gene AtST2a from Arabidopsis thaliana encodes a hydroxyjasmonate sulfotransferase. The recombinant AtST2a protein was found to exhibit strict specificity for 11-and 12-hydroxyjasmonate with K m values of 50 and 10 M, respectively. Furthermore, 12-hydroxyjasmonate and its sulfonated derivative are shown to be naturally occurring in A. thaliana. The exogenous application of methyljasmonate to A. thaliana plants led to increased levels of both metabolites, whereas treatment with 12-hydroxyjasmonate led to increased level of 12-hydroxyjasmonate sulfate without affecting the endogenous level of jasmonic acid. AtST2a expression was found to be induced following treatment with methyljasmonate and 12-hydroxyjasmonate. In contrast, the expression of the methyljasmonate-responsive gene Thi2.1, a marker gene in plant defense responses, is not induced upon treatment with 12-hydroxyjasmonate indicating the existence of independent signaling pathways responding to jasmonic acid and 12-hydroxyjasmonic acid. Taken together, the results suggest that the hydroxylation and sulfonation reactions might be components of a pathway that inactivates excess jasmonic acid in plants. Alternatively, the function of AtST2a might be to control the biological activity of 12-hydroxyjasmonic acid.

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Sorghum SbSTS1 was the first example of a stilbene synthase gene in monocots. Previously, we demonstrated that the gene was involved in defense responses. To examine its biochemical function in planta, SbSTS1 was overexpressed in transgenic Arabidopsis. Metabolite analysis revealed that cis-resveratrol glucoside (piceid) accumulated as the major stilbene in the transgenic lines. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in selected reaction monitoring mode, up to 580 microg g(-1) FW of cis-piceid were detected in 2-week-old plants, which represent a convenient source of the cis-isomers for pharmacological investigations. Our results also suggested the presence of unknown stilbene isomerase activities in Arabidopsis.

A conformational analysis of the valine side chains of ribonuclease T1 (RNase T1) was performed using NMR spectroscopy, in particular homonuclear (1H, 1H and 13C, 13C) and heteronuclear (1H, 15N and 1H, 13C) vicinal spin-spin coupling constants as obtained from E.COSY-type NMR experiments. The coupling constants related to the chi 1 dihedral angle in valine, 3JH alpha H beta, 3JNH beta, 3JC'H beta, 3JH alpha C gamma 1, 3JH alpha C gamma 2, 3JC'C gamma 1, and 3JC'C gamma 2, were evaluated in a quantitative manner. The analysis of 3J data allowed for the stereospecific assignment of the valine methyl resonances. On the basis of various models for motional averaging of coupling constants, a fit of the torsion angles chi 1 to a set of the experimental 3J coupling constants (3JH alpha H beta, 3JNH beta, 3JC'H beta) was carried out. The resulting side-chain conformations were examined with respect to NOE distance informations. Single rotameric states emerged for Val16, Val67, Val79, and Val101, while conformational equilibria between staggered rotamers were found for Val33 and Val78. Using a different model approach, Val52 and Val89 are also likely to exhibit unimodal chi 1 angle distributions. The analysis was found to depend critically on the set of Karplus parameters used. Except for Val52 and Val78, the predominant rotamers obtained from 3J coupling informations agree with the conformation in the crystal structure of ribonuclease T1 (Martinez-Oyanedel et al., 1991).

In the search for non-traditional seed oils, physicochemical parameters, fatty acid (FA) and triacylglycerol (TAG) profiles for five Botswana seed oils, obtained by Soxhlet extraction, were determined. GC-MS and 1 H-NMR analyses showed the FA profiles for mkukubuyo, Sterculia africana, and manketti, Ricinodendron rautanenii, seed oils dominated by linoleic and oleic acids, 26.1, 16.7 and 51.9, 24.4%, respectively, with S. africana containing significant amounts of cyclic FAs (19.9%). Mokolwane, Hyphaene petersiana, seed oil was typically lauric; 12:0 and 14:0 acids were 25.9 and 13.4%, respectively. Morama, Tylosema esculentum, seed oil resembled olive oil; 18:1 (47.3%) and 18:2 (23.4%) acids dominated. Moretologa-kgomo, Ximenia caffra, seed oil had 45.8% of 18:1 FA, plus significant amounts of very long chain FAs: 26:1 (5.8%), 28:1 (13.9%), 30:1 (3.9%), and acetylenic acids, 9a-18:1 (1.5%) and 9a, 11t-18:2 (16.0%). TAG classes and regiochemistry were determined with ESI-FTICR-MS, and 13 C-NMR spectra, respectively. Morama showed seven major TAG classes with C54:4 and C54:3 dominating; mokolwane had 16 major classes with C32:0, C38:0 and C42:2 dominating; manketti had 11 major classes with C54:7, C54:6 and C54:4 dominating; mkukubuyo had 12 major classes with C52:4, C52:3 and C54:4 dominating; moretologa-kgomo had 30 major TAG classes with C64:5, C64:3 and C62:3 dominating. Saturated FAs were generally distributed over the sn-1(3) position for morama, manketti, and moretologa-kgomo but at the sn-2 position for mokolwane and mkukubuyo. These findings indicate that morama and manketti seed oils can be developed for food uses, whilst moretologa-kgomo and mkukubuyo seed oils only for nonfood uses.

The phytosterol, tocopherol, and tocotrienol profiles for mkukubuyo, Sterculia africana, manketti, Ricinodendron rautanenni, mokolwane, Hyphaene petersiana, morama, Tylosema esculentum, and moretologa-kgomo, Ximenia caffra, seed oils from Botswana have been determined. Normal-phase HPLC analysis of the unsaponifiable matter showed that among the selected oils, the most abundant tocopherol and tocotrienol were c-tocopherol (2232.99 lg/g)