Teruhiko Yoshihara

Potato tuber-inducing activities of jasmonic acid and related compounds

Salicylic acid (SA) induced potato tuberization in vitro at concentrations greater than 10−5 M. A comparison of the tuber-inducing activities of various related compounds suggested that derivatives of benzoic acid with a free carboxyl group and a substituent at the C-2 position of the benzene ring have this activity. Although SA had the strongest activity among the compounds tested, the activity was about one thousandth of that of natural jasmonic acid (1R,2S-jasmonic acid) in terms of the threshold concentration for activity. Spraying SA to leaves of plants grown under tuber-noninducing conditions (long days) induced tuberization. However, the natural occurrence of SA was not detected in the leaves of potato plants that had been grown under tuber-inducing conditions (short days) and had begun to form tubers. The results seem to exclude the possibility of the involvement of SA in the natural tuberization of potato plants.

Distribution and chemical speciation of aluminum in the Al accumulator plant, Melastoma malabathricum L.

The Al accumulation mechanisms in an Al accumulator plant, Melastoma malabathricum L. (Melastoma), was investigated. Al was located in the upper epidermal cells and also distributed in mesophyll cells in leaf sections. In root sections, Al was found in all the root tissues, particularly in the epidermis and endodermis. Al concentrations in young leaves, mature leaves, old leaves, and roots were 8.0, 9.2, 14.4, and 10.1 mg g1, respectively. Approximately 45% of total Al in oldest leaves, and approximately 60% of total Al in leaves of other positions and roots were extracted in Tris-HCl buffer (pH 7.0). Since Al in the residual parts was mostly dissolved in hot 0.5 M H2SO4 containing 2% cetyl trimethylammonium bromide, residual Al seemed to consist mainly of monomeric Al and Al bound to pectic substances and hemicellulose. Al in the Tris-HCl extract consisted of non-monomeric Al (complexed form). Oxalate concentration in the Tris-HCl extract in leaves was significantly higher in the +Al treatment than in the –Al treatment and there was a positive correlation between the Al concentration and oxalate concentration. 27Al NMR spectrum of fresh leaves indicated the presence in the order of monomeric Al, Al-oxalate, Al-(oxalate)2, and Al-(oxalate)3 in intact leaves.

Four fungitoxic C-18 hydroxy unsaturated fatty acids from stromata of epichloe typhina

Abstract Four fungitoxic C-18 hydroxy unsaturated fatty acids ( 1 )–( 4 ) have been isolated from stromata of Epichloe typhina . Their structures including the absolute configuration have been elucidated from spectral data.

DPPH Radical Scavengers from Dried Leaves of Oregano (Origanum vulgare)

1,1-Dipehnyl-2-picrylhydrazyl (DPPH) radical scavenging activities were found in the extract of dried leaves of oregano (Origanum vulgare). The water-soluble active ingredients were isolated, and their structures were determined to be 4′-O-β-D-glucopyranosyl-3′,4′-dihydroxybenzyl protocatechuate and 4′-O-β-D-glucopyranosyl-3′,4′-dihydroxybenzyl 4-O-methylprotocatechuate by 1H-, 13C-NMR, DEPT, HMQC, and HMBC spectral analyses, and by NOE experiments. The DPPH radical scavenging activities of these compounds were compared with those of rutin, quercetin and rosmarinic acid at a concentration of 2×10-5 M. The scavenging activity of 4′-O-β-D-glucopyranosyl-3′,4′-dihydroxybenzyl protocatechuate was almost the same as that of quercetin and rosmarinic acid, but that of 4′-O-β-D-glucopyranosyl-3′,4′-dihydroxybennzyl 4-O-methylprotocatechuate was less than that of quercetin, rosmarinic acid and 4′-O-β-D-glucopyranosyl-3′,4′-dihydroxybenzyl protocatechuate. The amount of 4′-O-β-D-glucopyranosyl-3′,4′-dihydroxybenzyl protocatechuate was estimated to be 3.8 mg/1 g of dried leaves by an HPLC analysis.

Coronatine, a Bacterial Phytotoxin, acts as a Stereospecific Analog of Jasmonate Type Signals in Tomato Cells and Potato Tißues

Summary Coronatine was investigated in order to find its primary target in the biosynthesis of ethylene in cell suspension cultures of Lycopersicon peruvianum (L. p.) and Lycopersicon esculentum (L. e.). A stimulation of the ethylene forming enzyme (EFE) beginning after 30 to 60 minutes of the experiments and a decrease of the endogenous ACC-pool beginning after about 2 hours were detected, but could not be shown to be the primary effect of the toxin. Methyl jasmonate (Ja-Me) was tested in the same kind of experiments because of structural similarities with coronatine and gave effects similar to the toxin in contrast to auxin. Methyl (+)-epijasmonate was separated from its three other stereoisomers to confirm the structure activity relationship according to coronatine. Typical biotests for the toxin (hypertrophy of potato tuber tisue) as well as for the plant growth regulator (tuber induction at potato stolons) showed similar effects of coronatine and jasmonates in every case. Some structurally related compounds were tested in the cell culture system and implications for the mode of action are discused.

Potato micro-tuber inducing substances from Lasiodiplodia theobromae

Abstract Three potato-tuber inducing substances were isolated from Lasiodiplodia theobromae IFO 31059, and their structures identified as mellein, jasmonic acid and a previously unrecorded cyclohexene named theobroxide.

Structural identification of cepaciamide A, a novel fungitoxic compound from Pseudomonas cepacia D-202

A novel fungitoxic compound, cepaciamide A, was isolated from Pseudomonas cepacia D-202. Its structure and stereochemistry were elucidated by the spectroscopic and synthetic methods.

Jasmonate-inducible expression of a potato cathepsin D inhibitor-GUS gene fusion in tobacco cells

A potato gene encoding cathepsin D inhibitor (CDI) is expressed constitutively in tubers and flower buds and it is inducible in leaves upon wounding of the tissue or by treatment with methyl jasmonate (MJA). A fusion gene (CDI:GUS) in which the 2.4 kb long promoter of the CDI gene was translationaly fused with the coding sequence for β-glucuronidase (GUS) showed MJA-inducible expression in transformed tobacco cells in suspension. The maximum level of induction by MJA was obtained in the absence of auxin and repression of MJA-inducible expression of the fusion gene by auxin was released by aphidicolin, the results suggesting that MJA-inducible expression is repressed during active cell division. JA and MJA showed similar activities in inducing the expression of the fusion gene, while other JA-related compounds such as cucurbic acid, tuberonic acid and dihydrojasmonic acid neither induced expression of the fusion gene nor inhibited the MJA-inducible expression of the fusion gene. Methyl dihydrojasmonate specifically stimulated the MJA-inducible expression of the fusion gene. The MJA-inducible expression of the fusion gene was observed even with a 100 bp long promoter of the CDI gene albeit with significantly decreased level of expression compared to the 2.4 kb long promoter. The 100 bp long CDI promoter did not contain a G-box or hexamer motif that had been implicated in the MJA-responsive expression of several other plant genes. Further mutagenesis of the 100 bp long promoter by deletion or oligonucleotide insertion suggested that although a sequence between −100 and −82 is required for the MJA-responsive expression, the presence of this sequence alone does not confer the MJA-responsive expression.

Dissolution of ferric phosphate by alfalfa (Medicago sativa L.) root exudates

Alfalfa (Medicago sativa L.) was grown in hydroponic culture to investigate adaptation to Fe-deficiency. Root exudates released into the nutrient solution from Fe-deficient plants were trapped and condensed on an amberlite XAD-4 resin column. The diethyl ether fraction of these exudates dissolved ferric phosphate remarkably. The dissolving capability was about 62 times higher than that of root exudates obtained from Fe-sufficient plants in complete nutrient solution. The Fe-dissolving compound was separated and identified. It was a new natural compound with molecular formula C14H10O5 and was identified as 2-(3’,5’-dihydroxyphenyl)-5,6-dihydroxybenzofuran by means of mass spectrometry and 1 H-nuclear magnetic resonance. This new compound worked as a phytoalexin and inhibited completely the fungal growth of Fusarium oxysporum f. sp. phaseoli.

Three phenolic acid derivatives from stromata of Epichloe typhina on Phleum pratense

Abstract Three new phenolic acid derivatives, 1,3- O -di- trans - p -coumaroylglycerol, 1,2- O -di- trans - p -coumaroylglycerol and chokorin were isolated from stromata of Epichloe typhina on timothy plants Phleum pratense . Their structures were established by spectroscopic and chemical means.