Ryo Nakano

Copolymerization of Propylene and Polar Monomers Using Pd/IzQO Catalysts

Palladium catalysts bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands polymerize α-olefins while incorporating polar monomers. The steric environment provided by N-heterocyclic-carbene (NHC) enables regioselective insertion of α-olefins and polar monomers, yielding polypropylene, propylene/allyl carboxylate copolymers, and propylene/methyl acrylate copolymer. Known polymerization catalysts bearing NHC-based ligands decompose rapidly, whereas the present catalyst is durable because of structural confinement, wherein the NHC-plane is coplanar to the metal square plane. The present catalyst system enables facile access to a new class of functionalized polyolefins and helps conceive a new fundamental principle for designing NHC-based ligands.

Moths produce extremely quiet ultrasonic courtship songs by rubbing specialized scales

Insects have evolved a marked diversity of mechanisms to produce loud conspicuous sounds for efficient communication. However, the risk of eavesdropping by competitors and predators is high. Here, we describe a mechanism for producing extremely low-intensity ultrasonic songs (46 dB sound pressure level at 1 cm) adapted for private sexual communication in the Asian corn borer moth, Ostrinia furnacalis. During courtship, the male rubs specialized scales on the wing against those on the thorax to produce the songs, with the wing membrane underlying the scales possibly acting as a sound resonator. The males song suppresses the escape behavior of the female, thereby increasing his mating success. Our discovery of extremely low-intensity ultrasonic communication may point to a whole undiscovered world of private communication, using “quiet” ultrasound.

Copolymerization of carbon dioxide and butadiene via a lactone intermediate

Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its use as a monomer in copolymerization with olefins has long been an elusive endeavour. A major obstacle for this process is that the propagation step involving carbon dioxide is endothermic; typically, attempted reactions between carbon dioxide and an olefin preferentially yield olefin homopolymerization. Here we report a strategy to circumvent the thermodynamic and kinetic barriers for copolymerizations of carbon dioxide and olefins by using a metastable lactone intermediate, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, which is formed by the palladium-catalysed condensation of carbon dioxide and 1,3-butadiene. Subsequent free-radical polymerization of the lactone intermediate afforded polymers of high molecular weight with a carbon dioxide content of 33 mol% (29 wt%). Furthermore, the protocol was applied successfully to a one-pot copolymerization of carbon dioxide and 1,3-butadiene, and one-pot terpolymerizations of carbon dioxide, butadiene and another 1,3-diene. This copolymerization technique provides access to a new class of polymeric materials made from carbon dioxide. Radical polymerization of a metastable lactone intermediate — formed from carbon dioxide and butadiene using a palladium catalyst — produces a high-CO2-content (29 wt%) polymer. This approach circumvents the thermodynamic and kinetic barriers typically associated with direct copolymerization of carbon dioxide and olefins, and can also be applied to one-pot co- and terpolymerization of carbon dioxide and 1,3-butadienes.

Pheromone-gland-specific fatty-acyl reductase in the adzuki bean borer, Ostrinia scapulalis (Lepidoptera: Crambidae)

The adzuki bean borer moth, Ostrinia scapulalis, uses a mixture of (E)-11- and (Z)-11-tetradecenyl acetates as a sex pheromone. At a step in the pheromone biosynthetic pathway, fatty-acyl precursors are converted to corresponding alcohols by an enzyme, fatty-acyl reductase (FAR). Here we report the cloning of FAR-like genes expressed in the pheromone gland of female O. scapulalis, and the characterization of a single pheromone-gland-specific FAR (pgFAR) and its functional assay using an insect cell expression system. As many as thirteen FAR-like genes (FAR-I-FAR-XIII) were expressed in the pheromone gland of O. scapulalis; however, only one (FAR-XIII) was pheromone-gland-specific. The deduced amino acid sequence of FAR-XIII predicted a 462-aa protein with a conserved NAD(P)H-binding motif in the N-terminal region, showing overall identity of 34% with the pgFAR of Bombyx mori. A functional assay using Sf9 cells transfected with an expression vector containing the open reading frame of the FAR-XIII gene has proven that FAR-XIII protein has the ability to convert a natural substrate, (Z)-11-tetradecenoic acid, to a corresponding alcohol, (Z)-11-tetradecenol.

Moths are not silent, but whisper ultrasonic courtship songs

SUMMARY Ultrasonic hearing is widespread among moths, but very few moth species have been reported to produce ultrasounds for sexual communication. In those that do, the signals are intense and thus well matched for long distance communication. By contrast, males of the Asian corn borer moth (Crambidae) were recently shown to whisper extremely low-intensity ultrasonic courtship songs close to females. Since low sound levels will prevent eavesdropping by predators, parasites and conspecific rivals, we predicted low intensity ultrasound communication to be widespread among moths. Here we tested 13 species of moths including members of the Noctuidae, Arctiidae, Geometridae and Crambidae. Males of nine species, 70%, produced broadband ultrasound close to females. Peak frequencies ranged from 38 to above 100 kHz. All sounds were of low intensity, 43-76 dB SPL at 1 cm [64±10 dB peSPL (mean ± s.d.), N=9 species]. These quiet and/or hyper-frequency ultrasounds are audible to nearby mates, but inaudible to unintended receivers. Although largely unknown because it is so inconspicuous, acoustic communication using low intensity ultrasound appears to be widespread among hearing moths. Thus, acoustic communication may be the norm rather than the exception.

Copolymerization of Ethylene and Polar Monomers by Using Ni/IzQO Catalysts.

The replacement of precious metals in catalysis by earth-abundant metals is currently one of the urgent challenges for chemists. Whereas palladium-catalyzed copolymerization of ethylene and polar monomers is a valuable method for the straightforward synthesis of functionalized polyolefins, the corresponding nickel-based catalysts have suffered from poor thermal tolerance and low molecular weight of the polymers formed. Herein, we report a series of neutral nickel complexes bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands. The Ni/IzQO system can catalyze ethylene polymerization at 50-100 °C with reasonable activity in the absence of any cocatalyst, whereas most known nickel-based catalysts are deactivated at this temperature range. The Ni/IzQO catalyst was successfully applied to the copolymerization of ethylene with allyl monomers to obtain the corresponding copolymers with the highest molecular weight reported for a Ni-catalyzed system.

Sex-linked pheromone receptor genes of the European corn borer, Ostrinia nubilalis, are in tandem arrays.

Background Tuning of the olfactory system of male moths to conspecific female sex pheromones is crucial for correct species recognition; however, little is known about the genetic changes that drive speciation in this system. Moths of the genus Ostrinia are good models to elucidate this question, since significant differences in pheromone blends are observed within and among species. Odorant receptors (ORs) play a critical role in recognition of female sex pheromones; eight types of OR genes expressed in male antennae were previously reported in Ostrinia moths. Methodology/Principal Findings We screened an O. nubilalis bacterial artificial chromosome (BAC) library by PCR, and constructed three contigs from isolated clones containing the reported OR genes. Fluorescence in situ hybridization (FISH) analysis using these clones as probes demonstrated that the largest contig, which contained eight OR genes, was located on the Z chromosome; two others harboring two and one OR genes were found on two autosomes. Sequence determination of BAC clones revealed the Z-linked OR genes were closely related and tandemly arrayed; moreover, four of them shared 181-bp direct repeats spanning exon 7 and intron 7. Conclusions/Significance This is the first report of tandemly arrayed sex pheromone receptor genes in Lepidoptera. The localization of an OR gene cluster on the Z chromosome agrees with previous findings for a Z-linked locus responsible for O. nubilalis male behavioral response to sex pheromone. The 181-bp direct repeats might enhance gene duplications by unequal crossovers. An autosomal locus responsible for male response to sex pheromone in Heliothis virescens and H. subflexa was recently reported to contain at least four OR genes. Taken together, these findings support the hypothesis that generation of additional copies of OR genes can increase the potential for male moths to acquire altered specificity for pheromone components, and accordingly, facilitate differentiation of sex pheromones.

Variation in Courtship Ultrasounds of Three Ostrinia Moths with Different Sex Pheromones

Moths use ultrasounds as well as pheromones for sexual communication. In closely related moth species, variations in ultrasounds and pheromones are likely to profoundly affect mate recognition, reproductive isolation, and speciation. The European corn borer, Ostrinia nubilalis, and its Asian congeners, Ostrinia furnacalis and Ostrinia scapulalis, exhibit within-species and between-species variation in their pheromone communication. Recently, we reported ultrasound communication in O. furnacalis; however, variations in ultrasounds in the three congeners have not been addressed to date. Here we investigated features of ultrasound production and hearing in O. nubilalis and O. scapulalis, and compared them with those of O. furnacalis. As in O. furnacalis, males of O. nubilalis and O. scapulalis produced ultrasounds during courtship by rubbing specialized scales on the wings against scales on the thorax. The covering of these scales with nail polish muffled the sounds and significantly reduced mating success in O. nubilalis, showing the importance of ultrasound signaling in mating. The ultrasounds produced by O. nubilalis and O. scapulalis were similar, consisting of long trains of pairs of pulses with a main energy at 40 kHz, but distinctly different from the ultrasound produced by O. furnacalis, consisting of groups of pulses peaking at 50 kHz and with substantially more energy up to 80 kHz. Despite overall similarities, temporal features and patterns of amplitude modulation differed significantly among the geographic populations of O. nubilalis and O. scapulalis, which differed in pheromone type. In contrast, no significant difference in hearing was found among the three species with regard to the most sensitive frequencies and hearing threshold levels. The patterns of variations in the songs and pheromones well reflected those of the phylogenetic relationships, implying that ultrasound and pheromone communications have diverged concordantly. Our results suggest that concordant evolution in sexual signals such as courtship ultrasounds and sex pheromones occurs in moths.

Ultrasonic courtship songs of male Asian corn borer moths assist copulation attempts by making the females motionless.

Males of the Asian corn borer moth Ostrinia furnacalis (Guenée) produce an ultrasonic courtship song of extremely low‐intensity during copulation attempts. The song has been shown to significantly increase the mating success of the male; however, the mode of action of the sound in courtship remains to be resolved. Behavioural experiments using pairs with deafened females or muted males show that, without the aid of the sound, 63% of males eventually succeed in mating after several copulation attempts, whereas the remainder (37%) make repeated attempts in vain until interrupted by the escape of the female. Because few (2%) males fail to copulate when females hear the courtship song, it is evident that the song has an effect on females, promoting the success of copulation attempts. In support of this view, males produce louder songs if the first copulation attempt fails, suggesting that the males increase their sound levels to achieve successful copulation. It is suggested that the ultrasonic songs of the male render the females motionless, which is the same response as that to ultrasonic bat calls. Because even slight movements by the female can interfere with the attempt of the male to copulate, it is likely that, by making her motionless, the success rate of a single copulation attempt is increased greatly.

Female sex pheromone of a lichen moth Eilema japonica (Arctiidae, Lithosiinae): components and control of production.

Seven candidates for components of the female sex pheromone of Eilema japonica (Arctiidae, Lithosiinae) were detected in an extract of pheromone glands with a gas chromatograph-electroantennographic detector. The compounds were identified as (Z,Z)-6,9-icosadiene (D20), (Z,Z)-6,9-henicosadiene (D21), (Z,Z,Z)-3,6,9-henicosatriene (T21), (Z,Z)-6,9-docosadiene (D22), (Z,Z,Z)-3,6,9-docosatriene (T22), (Z,Z)-6,9-tricosadiene (D23), and (Z,Z,Z)-3,6,9-tricosatriene (T23). Assays using synthetic lures in a wind tunnel showed that D21 (proportion, 0.39), T21 (0.08), D22 (0.27), and T22 (0.26) are important for evoking full behavioral responses from the males. Titers of the pheromone components did not show clear temporal fluctuations. Moreover, decapitation of the female moth had no effect on the titers of pheromone components in the pheromone gland, suggesting that cephalic endocrine factors such as pheromone biosynthesis activating neuropeptide (PBAN) are not involved in the control of pheromone biosynthesis in this species.