Congenital right ventricular diverticulum formed by pulmonary regurgitative jet flow in a fetus with tetralogy of Fallot and absent pulmonary valve.

Congenital ventricular diverticulum is a rare anomaly with an unclear pathology. Here, we report a male fetus at 24 weeks of gestation, diagnosed with right ventricular diverticulum associated with tetralogy of Fallot and absent pulmonary valve. The diverticulum was located at the anterosuperior wall of the right ventricle and faced into the massive pulmonary regurgitation flow jet. Intrauterine fetal death from heart failure resulted at 26 weeks of gestation. An autopsy revealed significant subendocardial fibrosis in the diverticular wall without inflammatory cell infiltration. Clinical and pathologic features suggested that the regurgitative blood flow contributed to the formation of the right ventricular diverticulum.

Effects of a bile acid elicitor, cholic acid, on the biosynthesis of diterpenoid phytoalexins in suspension-cultured rice cells.

An elicitor of rice defense responses was recently isolated from human feces and was identified as cholic acid (CA). Pathogen infection in rice leaves induces phytocassanes and momilactones, both of which are major diterpenoid phytoalexins in rice, whereas CA mainly induces phytocassanes. We established a high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry protocol for the rapid and accurate quantification of phytocassanes and momilactones. Using this method, we showed that CA preferentially induced the formation of phytocassanes in suspension-cultured rice cells, while a fungal chitin oligosaccharide elicitor induced that of both phytocassanes and momilactones. We further investigated the effects of CA on the expression of diterpene cyclase genes involved in phytoalexin biosynthesis. CA induced the transcription of the genes OsCPS2 (OsCyc2) and OsKSL7 (OsDTC1), which are involved in phytocassane biosynthesis, to a greater extent than the genes OsCPS4 (OsCyc1) and OsKSL4, which are involved in momilactone biosynthesis. OsCPS2 was particularly strongly induced, suggesting that it is one of the main mechanisms by which CA induces high levels of phytocassanes.

Identification of a biosynthetic gene cluster in rice for momilactones.

Rice diterpenoid phytoalexins such as momilactones and phytocassanes are produced in suspension-cultured rice cells treated with a chitin oligosaccharide elicitor and in rice leaves irradiated with UV light. The common substrate geranylgeranyl diphosphate is converted into diterpene hydrocarbon precursors via a two-step sequential cyclization and then into the bioactive phytoalexins via several oxidation steps. It has been suggested that microsomal cytochrome P-450 monooxygenases (P-450s) are involved in the downstream oxidation of the diterpene hydrocarbons leading to the phytoalexins and that a dehydrogenase is involved in momilactone biosynthesis. However, none of the enzymes involved in the downstream oxidation of the diterpene hydrocarbons have been identified. In this study, we found that a putative dehydrogenase gene (AK103462) and two functionally unknown P-450 genes (CYP99A2 and CYP99A3) form a chitin oligosaccharide elicitor- and UV-inducible gene cluster, together with OsKS4 and OsCyc1, the diterpene cyclase genes involved in momilactone biosynthesis. Functional analysis by heterologous expression in Escherichia coli followed by enzyme assays demonstrated that the AK103462 protein catalyzes the conversion of 3beta-hydroxy-9betaH-pimara-7,15-dien-19,6beta-olide into momilactone A. The double knockdown of CYP99A2 and CYP99A3 specifically suppressed the elicitor-inducible production of momilactones, strongly suggesting that CYP99A2, CYP99A3, or both are involved in momilactone biosynthesis. These results provide strong evidence for the presence on chromosome 4 of a gene cluster involved in momilactone biosynthesis.

Involvement of the basic helix-loop-helix transcription factor RERJ1 in wounding and drought stress responses in rice plants.

The jasmonic acid (JA)-responsive gene RERJ1 isolated from suspension-cultured rice cells encodes a transcription factor with a basic helix-loop-helix motif. In this study, we found that RERJ1 is also expressed in rice plants in response to JA, and that its expression in rice leaves is up-regulated by exposure to wounding and drought stress. It is also suggested that JA but not abscisic acid is involved in the up-regulation of RERJ1 expression caused by wounding and drought stress.

Preparation and biological activity of molecular probes to identify and analyze jasmonic acid-binding proteins.

Several types of jasomonic acid (JA) derivatives, including JA--amino acid conjugates, a JA--biotin conjugate, a JA--dexamethasone heterodimer, and a JA-fluoresceine conjugate, were prepared as candidates for molecular probes to identify JA--binding proteins. These JA derivatives, excepting the JA--fluoresceine conjugate, exhibited significant biological activities in a rice seedling assay, a rice phytoalexin-inducing assay, and/or a soybean phenylalanine ammonia-lyase-inducing assay. These JA derivatives could therefore be useful probes for identifying JA--binding proteins. The activity spectra of the prepared compounds were different from each other, suggesting that different types of JA receptors were involved in the perception of JA derivatives in the respective bioassays.

Dihydrocoronatine, promising candidate for a chemical probe to study coronatine-, jasmonoid- and octadecanoid-binding protein.

Coronatine (1), its synthetic analogs (6-13) and jasmonic acid induced various volatiles in rice leaves. In the range of 0.01-0.1 mM, dihydrocoronatine (7) exhibited 4-687 times higher activity for linalool emission than that of 1. The radioactive derivative of 7, [4,5-3H]-7, was employed to identify the putative coronatine-binding protein in rice leaves. 7 would be a promising candidate for a chemical probe to study cornatine-binding protein related to the jasmonoid and octadecanoid signaling pathway in higher plants. A detailed study of coronatine-binding protein in rice leaves and cell culture with [4,5-3H]-7 is now in progress.

Response of Saccharomyces cerevisiae to a monoterpene: evaluation of antifungal potential by DNA microarray analysis.

Plant-derived essential oils with monoterpenoids have been used as antifungal drugs since ancient times, but the mode of action of these natural hydrocarbons at the molecular level is not understood. In order to understand the mechanisms of toxicity of alpha-terpinene (a cyclic monoterpene), a culture of Saccharomyces cerevisiae was exposed to 0.02% alpha-terpinene for 2 h and transcript profiles were obtained using yeast DNA arrays. These profiles, when compared with transcript profiles of untreated cultures, revealed that the expression of 793 genes was affected. For 435 genes, mRNA levels in treated cells compared with control cells differed by more than two-fold, whereas for 358 genes, it was <0.5-fold. Northern blots were performed for selected genes to verify the microarray results. Functional analysis of the up-regulated genes indicates that, similar to commonly used antifungal drugs, alpha-terpinene exposure affected genes involved in ergosterol biosynthesis and sterol uptake. In addition, transcriptional induction of genes related to lipid metabolism, cell wall structure and function, detoxification and cellular transport was observed in response to terpinene toxicity. Notably, the functions of 192 up-regulated genes are still unknown, but their characterization will probably shed light on the mechanisms of drug resistance and sensitivity. Taken together, this study showed that alpha-terpinene has strong antifungal activities and its modes of action resemble those of presently used antifungal drugs.

Enhanced resistance to blast fungus and bacterial blight in transgenic rice constitutively expressing OsSBP, a rice homologue of mammalian selenium-binding proteins.

The rice Oryza sativa selenium-binding protein homologue (OsSBP) gene encodes a homologue of mammalian selenium-binding proteins, and it has been isolated as one of the genes induced by treating a plant with a cerebroside elicitor from rice blast fungus. The possible role of OsSBP in plant defense was evaluated by using a transgenic approach. Plants overexpressing OsSBP showed enhanced resistance to a virulent strain of rice blast fungus as well as to rice bacterial blight. The expression of defense-related genes and the accumulation of phytoalexin after infection by rice blast fungus were accelerated in the OsSBP overexpressors. A higher level of H(2)O(2) accumulation and reduced activity of such scavenging enzymes as ascorbate peroxidase and catalase were seen when the OsSBP-overexpressing plants were treated with the protein phosphatase 1 inhibitor, calyculin A. These results suggest that the upregulation of OsSBP expression conferred enhanced tolerance to different pathogens, possibly by increasing plant sensitivity to endogenous defense responses. Additionally, the OsSBP protein might have a role in modulating the defense mechanism to biotic stress in rice.

Purification and identification of antimicrobial sesquiterpene lactones from yacon (Smallanthus sonchifolius) leaves.

The extraction of yacon [Smallanthus sonchifolius (Poepp. and Endl.) H. Robinson; Asteraceae] leaves and chromatographic separation yielded two new antibacterial melampolide-type sesquiterpene lactones, 8beta-tigloyloxymelampolid-14-oic acid methyl ester and 8beta-methacryloyloxymelampolid-14-oic acid methyl ester, as well as the four known melampolides, sonchifolin, uvedalin, enhydrin and fluctuanin. The newly identified compound, 8beta-methacryloyloxymelampolid-14-oic acid methyl ester, exhibited potent antimicrobial activity against Bacillus subtilis and Pyricularia oryzae, while 8beta-tigloyloxymelampolid-14-oic acid methyl ester showed lower activity. Fluctuanin exhibited the strongest antibacterial activity against B. subtilis among these six sesquiterpene lactones.

Synthesis of the (17R)- and (17S)-isomers of volicitin, an elicitor of plant volatiles contained in the oral secretion of the beet armyworm.

Both the (17R)- and (17S)-isomers of volicitin, which is contained in the oral secretion of the beet armyworm and induces corn seedlings to emit a blend of volatile compounds to attract the natural enemy of the herbivore, were synthesized via the semi-hydrogenation of an intermediary diyne and (Z)-selective olefination as the key steps. They were both obtained as crystalline compounds.

Biosynthesis of rice phytoalexin: enzymatic conversion of 3beta-hydroxy-9beta-pimara-7,15-dien-19,6beta-olide to momilactone A.

Momilactone A, a major rice diterpene phytoalexin, could be synthesized by dehydrogenation at the 3-position of 3beta-hydroxy-9beta-pimara-7,15-dien-19,6beta-olide in rice leaves. The presence of 3beta-hydroxy-9beta-pimara-7,15-dien-19,6beta-olide in UV-irradiated rice leaves was confirmed by comparing the mass spectra and retention times after a GC/MS analysis of the natural and synthetic compounds. The soluble protein fraction from UV-irradiated rice leaves showed dehydrogenase activity to convert 3beta-hydroxy-9beta-pimara-7,15-dien-19,6beta-olide into momilactone A. The enzyme required NAD+ or NADP+ as a hydrogen acceptor. The optimum pH for the reaction was 8. The Km value to 3beta-hydroxy-9beta-pimara-7,15-dien-19,6beta-olide was 36 microM when NAD+ was supplied as a cofactor at a concentration of 1 mM. 3fl-Hydroxy-9beta-pimara-7,15-dien-19,6beta-olide and its dehydrogenase activity were induced in a time-dependent manner by UV irradiation.

Induced volatiles in elicitor-treated and rice blast fungus-inoculated rice leaves.

The volatiles released from elicitor (copper chloride, jasmonic acid, UV, L-methionine and chitosan oligomer)-treated and rice blast fungus-inoculated rice leaves were collected by the solid-phase microextraction technique and analyzed by GC-MS. (Z)-3-Hexen-1-ol, monoterpenes, methyl salicylate, and sesquiterpenes were identified as elicitor-induced volatiles by a comparison of their GC retention times and mass spectra with those of authentic compounds. The different elicitors resulted in some qualitative and quantitative differences in the production of volatiles. Monoterpenes and sesquiterpenes were identified as the rice blast fungus-induced volatiles.