Novel potato micro-tuber-inducing compound, (3R,6S)-6-hydroxylasiodiplodin, from a strain of Lasiodiplodia theobromae.

A novel potato micro-tuber-inducing compound was isolated from the culture broth of Lasiodiplodia theobromae Shimokita 2. The structure of the isolated compound was determined as (3R,6S)-6-hydroxylasiodiplodin by means of spectroscopic analyses, the modified Mosher method, and chemical conversion. The compound showed potato micro-tuber-inducing activity at a concentration of 10−4 M, using the culture of single-node segments of potato stems in vitro

Novel antifungal compounds produced by Sterile Dark, an unidentified wheat rhizosphere fungus

Two novel antifungal compounds were isolated from a culture broth of Sterile Dark, an unidentified fungus isolated from the rhizosphere of wheat grown in a continuous cropping field. These compounds were elucidated to be phthalide-based compounds by spectroscopic analyses

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

Theobroxide inhibits stem elongation in Pharbitis nil by regulating jasmonic acid and gibberellin biosynthesis

In this study, exogenous factors affecting the elongation growth in the short day plant, Pharbitis nil, was investigated. Theobroxide inhibited stem elongation in Pharbitis nil both under short day (SD) and long day (LD) conditions. Salicylhydroxamic acid (SHAM), an inhibitor of jasmonic acid (JA) biosynthesis, and GA3 recovered the inhibitory effect of theobroxide on stem elongation. Quantitative analysis of JA showed that the level of endogenous JA increased significantly in theobroxide treated plants, while exogenously applied GA3 and SHAM suppressed JA biosynthesis stimulated by theobroxide. The activity of lipoxygenase (LOX, the key enzyme of JA biosynthesis) also was stimulated by theobroxide and this stimulation was nullified by SHAM and GA3. Quantitative analysis of GA1 showed that theobroxide suppressed GA1 biosynthesis. In non theobroxide treated Pharbitis nil, SD conditions stimulated JA biosynthesis and LOX activity, while GA1 biosynthesis was suppressed. All these results suggest that JA probably is involved negatively in the control of stem elongation, and the balance between JA and gibberellin might determine the stem growth in Pharbitis nil

Inhibition of stem elongation in spinach by theobroxide

In the current studies, we investigated the influences of theobroxide on stem elongation in spinach (Spinacia oleracea L.). Our results showed that stem elongation and flower formation were inhibited by spraying spinach plants with theobroxide under inductive, long day conditions (16 h light/8 h dark), while application of exogenous applied GA3 prevented the effect of theobroxide. Quantitative analysis showed that theobroxide suppressed GA1 biosynthesis, whereas the endogenous content of jasmonic acid was unchanged. However, under short day conditions (10 h light/14 h dark), there were no differences in stem length between treated and untreated plants. These results suggest that the inhibition of stem elongation by theobroxide is probably due to the suppression of gibberellin biosynthesis