Fumio Ihara

Aurovertins F-H from the Entomopathogenic Fungus Metarhizium anisopliae

Analysis of fermentation broth of the entomopathogenic fungus Metarhizium anisopliae has led to isolation of aurovertin D ( 1) and three new aurovertin-type metabolites, aurovertin F ( 2), aurovertin G ( 3), and aurovertin H ( 4). Their structures were determined on the basis of spectroscopic analyses and chemical conversions.

Identification of novel derivative of helvolic acid from Metarhizium anisopliae grown in medium with insect component.

Entomopathogenic fungi are unique owing to their versatile ability to produce many bioactive compounds and from the dependence of their morphological differentiation on the presence of insect-derived materials. An entomopathogenic fungus, Metarhizium anisopliae HF293, was found to show insect-material-dependent production of antibacterial compounds, which were purified to homogeneity from 10-d culture broth when the production reached maximum. Two compounds were isolated: the major compound was determined to be helvolic acid and the minor one was a novel derivative of helvolic acid (1,2-dihydrohelvolic acid). Discovery of a novel bioactive compound indicated that insect-derived material would be a useful factor for enhancing the diversity of compounds produced by entomopathogenic fungi.

Requirement in trans of the downstream limL gene for activation of lactonizing lipase from Pseudomonas sp. 109

Abstract A novel lipase (lactonizing lipase: lipL ) from Pseudomonas sp. 109 can catalyze synthesis of macrocyclic lactones in anhydrous organic solvents by transesterification. A gene situated immediately downstream from lipL was found to be essential for production of the functional lipase, and was denoted as limL ( li pase m odulator). Nucleotide sequence analysis of the limL region revealed a 340-amino acid open reading frame ( M r =37,658) 49 bp downstream from lipL . In the non-coding region between lipL and limL was situated a 32-base strong inverted repeat, and a putative ribosome binding site was present at 14 bases upstream from the limL initiator methionine. The deduced amino-acid sequence of LimL exhibited 29% overall homology with that of the lipase-modulator protein (LimA) of Pseudomonas cepacia . Although the homology itself was low, hydrophobicity/hydrophilicity plots of the two modulator proteins showed that the two proteins shared a similar hydropathy pattern, i.e. , the amino-terminus region is highly hydrophobic and the carboxyl-terminus region is strongly hydrophilic, suggesting that the two modulator proteins may activate corresponding lipase by similar functions. When lipL and limL were cloned separately in compatible plasmids, functional lipase was produced only in E. coli hosts harboring both the plasmids, indicating that limL can act in trans toward lipL .

Farinomalein, a maleimide-bearing compound from the entomopathogenic fungus Paecilomyces farinosus.

A new maleimide-bearing compound, farinomalein (1), was isolated from the entomopathogenic fungus Paecilomyces farinosus HF599. The structure was determined on the basis of spectroscopic analyses and chemical conversion. Compound 1 showed potent activity (5 mug/disk) against the plant pathogenic Phytophthora sojae P6497.

Cloning and functional analysis of the second geranylgeranyl diphosphate synthase gene influencing helvolic acid biosynthesis in Metarhizium anisopliae

A gene (ggs2) having high similarity to the geranylgeranyl diphosphate synthase (GGPP synthase) gene was cloned from Metarhizium anisopliae NAFF635007. The ggs2 gene (1,239-bp open reading frame with no intron) encoded a protein of 412 amino acids, and the transcription occurred only after late log-phase during the growth. Gene disruption of ggs2, performed to clarify the function in M. anisopliae, resulted in decreased GGPP synthase activity together with a slight delay of sporulation. An high performance liquid chromatography (HPLC) comparison of compound profiles between the wild-type strain and the disruptant revealed that a compound was abolished by the ggs2 disruption. Purification and structural elucidation by 1H-NMR and mass spectrometry analyses revealed that the lost compound is helvolic acid. Furthermore, the pathogenicity assay against two species of insect larvae revealed that the ggs2-disruptant possessed much weaker toxicity than the wild-type strain. Based on these results, it was concluded that ggs2 encodes the GGPP synthase influencing the biosynthesis of secondary metabolites in various species, including helvolic acid in M. anisopliae. To the best of our knowledge, this is the first report to identify a GGPP synthase gene related to secondary metabolism in entomopathogenic fungi.

Gene organization in the ada-rplL region of Streptomyces virginiae

The gene organization of a 7.4-kb region of the Streptomyces virginiae (Sv) chromosome was determined. The predicted open reading frames (ORFs) and their predicted products, in sequence order, were (i) ada, encoding adenosine deaminase [EC 3.5.4.4], (ii) aat, encoding a protein homologous to aspartate aminotransferase [EC 2.6.1.1], (iii) secE, encoding a protein involved in protein secretion, (iv) vbrA, encoding a NusG-like protein involved in antitermination of transcription as described by Okamoto et al. [J. Biol. Chem. 267 (1992) 1093-1098], and (v) rplKAJL, encoding the large subunits of the ribosomal proteins L11, L1, L10 and L12. Six of the ORFs (secE-rplL) were oriented in the same direction, but the other two (ada and aat) had the opposite orientation. The gene organization of the secE-rplL region in Sv was identical to that in Escherichia coli.

Ophiosetin, a new tetramic acid derivative from the mycopathogenic fungus Elaphocordyceps ophioglossoides.

Ophiosetin, a new tetramic acid derivative from the mycopathogenic fungus Elaphocordyceps ophioglossoides

Cyclic lipodepsipeptides verlamelin A and B, isolated from entomopathogenic fungus Lecanicillium sp.

Verlamelin and its new derivative (verlamelin B) were isolated from fermentation broth of entomopathogenic fungus Lecanicillium sp. HF627. As the structural elucidation of verlamelin so far was only preliminary, we studied and determined the absolute structure of these two compounds to be cyclo(5S-hydroxytetradecanoic acid-D-alloThr/Ser-D-Ala-L-Pro-L-Gln-D-Tyr-L-Val). This is the first study that precisely analyzed the structure of verlamelin.

Double meaning of courtship song in a moth

Males use courtship signals to inform a conspecific female of their presence and/or quality, or, alternatively, to ‘cheat’ females by imitating the cues of a prey or predator. These signals have the single function of advertising for mating. Here, we show the dual functions of the courtship song in the yellow peach moth, Conogethes punctiferalis, whose males generate a series of short pulses and a subsequent long pulse in a song bout. Repulsive short pulses mimic the echolocation calls of sympatric horseshoe bats and disrupt the approach of male rivals to a female. The attractive long pulse does not mimic bat calls and specifically induces mate acceptance in the female, who raises her wings to facilitate copulation. These results demonstrate that moths can evolve both attractive acoustic signals and repulsive ones from cues that were originally used to identify predators and non-predators, because the bat-like sounds disrupt rivals, and also support a hypothesis of signal evolution via receiver bias in moth acoustic communication that was driven by the initial evolution of hearing to perceive echolocating bat predators.

Production of antioomycete compounds active against the phytopathogens Phytophthora sojae and Aphanomyces cochlioides by clavicipitoid entomopathogenic fungi.

A total of 412 strains belonging to 14 genera of clavicipitoid entomopathogenic fungi (EPF) were screened for activities against two economically important plant pathogenic oomycetes, Phytophthora sojae and Aphanomyces cochlioides. To identify the antioomycete compounds produced by EPF, the extracts of 13 highly active EPF strains were characterized in detail by high performance liquid chromatography with diode array detection and high-resolution mass spectrometric detection and antioomycete assay. The antioomycete activity of several Metarhizium extracts was associated with previously isolated aurovertins, fungerin, N-(methyl-3-oxodec-6-enoyl)-2-pyrroline, and N-(methyl-3-oxodecanoyl)-2-pyrroline. The depsipeptide beauvericin was confirmed to be one of the active principles of three strains of Isaria tenuipes, which strongly inhibited mycelial growth of both P. sojae and A. cochlioides. Two known bioactive metabolites, paecilosetin and aranorosinol A, together with a novel and potent antioomycete compound, farinomalein, were isolated from the extracts of Isaria farinosa and all compounds were confirmed to have antioomycete activity. Identification of 8 antioomycete compounds from 13 clavicipitioid EPF demonstrated a new potential use of EPF as a source of compounds for the control of soil-borne plant pathogenic oomycetes.