Specific degradation ofβ-aryl ether linkage in synthetic lignin (dehydrogenative polymerizate) by bacterial enzymes ofSphingomonas paucimobilis SYK-6 produced in recombinantEscherichia coli

Sphingomonas paucimobilis SYK-6 produces unique and specific enzymes, such as-etherases,O-demethylases, and ring fission dioxygenases, for lignin degradation. Cleavage of arylglycerol--aryl ether linkage is the most important process in the lignin metabolic pathway ofS. paucimobilis SYK-6. We reported the genes (ligD, ligE, ligF) for enzymes that cleaved-aryl ether linkage of dimeric compounds in previous studies. In this study we synthesized the fluorescent high-molecular-weight lignin (UBE-DHP) by dehydrogenative polymerization. We investigated the-aryl ether cleavage ability of these enzymes produced in recombinantEscherichia coli. When UBE-DHP was incubated with LigF, 4-methylumbeliferone was released as a result of-aryl ether cleavage of O-methylumbelliferyl--hydroxypropiovanillone (compound III) incorporated in UBE-DHP. Here, we report that-etherase ofS. paucimobilis SYK-6 can be expressed inE. coli and is able to cleave the-aryl ether linkage in synthetic high-molecular-weight lignin.     

Foot rot disease of sweet potato in Japan caused by Diaporthe destruens: first report,pathogenicity and taxonomy

Journal of General Plant Pathology - Foot rot, also known as stem rot or tuber-root rot syndrome, on sweet potato occurs in sweet potato fields in Okinawa, Japan. Isolates of one fungal species...     

Yield and growth characteristics of erect panicle type rice (Oryza sativa L.) cultivar,Shennong265 under various crop management practices in Western Japan

Erect panicle rice cultivars utilize solar energy effectively and have improved ecological growing conditions. Among such cultivars, Shennong265 has been grown successfully throughout Northern China. Nevertheless, no studies have yet examined the relationships between crop dry matter productivity, weather conditions, and nitrogen uptake of the erect panicle type rice cultivar in Japan. The objective of our study was to evaluate the productivity of erect panicle rice Shennong265 in Western Japan under varied conditions. Three rice cultivars, Shennong265, Nipponbare, and Takanari were grown in the field under different fertilizer and plant density conditions in Western Japan; using this information, we compared yield and growth characteristics of Shennong265 with those of Nipponbare and Takanari. Although Shennong265 had radiation use efficiency similar to that of the high yielding cultivar (Takanari) and much higher leaf nitrogen content than Takanari and Nipponbare, the average grain yield of Shennong265 grown under normal fertilizer and plant density conditions was approximately 6.9 t ha^?1 as against 6.2 t ha^?1 for Nipponbare and 9.6 t ha^?1 for Takanari. These results suggest that, while Shennong265 has a high yield potential, the environmental conditions including climate, fertilizer, and planting period provided in this study were not suitable for achieving its maximum yield. The reduced performance of Shennong265 may be caused by insufficient fertilizer after heading and by shorter growth periods, as well as by the climate of Western Japan. Additional fertilizer application during the heading stage and earlier transplanting may be needed to obtain higher Shennong265 yields in Western Japan.     

pH- and temperature-dependent denaturation profiles of tuna myoglobin

Attempts have been made to elucidate the denaturation profiles of tuna myoglobin (Mb) in comparison with horse Mb. Intensive absorbance characterization was carried out for derivatives (deoxy, oxy, met forms) of Mb. The wavelength of the maximum absorbance of tuna Mb was shorter only by 1 nm for deoxy and metMb, while it was 4 nm shorter for the second peak of metMb. Percentage Mb denaturation (PMD) was measured under a combination of pH (5.6, 6.5, 7.4) and temperature (70, 75, 80 °C). Tuna Mb was almost completely denatured even during the initial incubation at 75 and 80 °C at all pHs examined. During the incubation at 70 °C, the PMD values for tuna Mb were 88.5, 52.1, and 67.7% at pH 5.6, 6.5, and 7.4, respectively. The denaturation of tuna Mb proceeded even at 55 °C, but denaturation rates were very slow at pH 6.5. On the other hand, horse Mb was found to be very stable at pH 6.5 and 7.4 at all temperatures examined, except at pH 6.5 and 80 °C. At pH 5.6, the PMD values of horse Mb gradually increased, especially at 75 and 80 °C. These different Mbs showed quite different denaturation profiles.     

Trichomes: interaction sites of tomato leaves with biotrophic powdery mildew pathogens

The present study aimed to explore the possibility of using the type I trichomes of tomato (Solanum lycopersicum) to monitor the infection processes of powdery mildews by microscopy. Individual trichome cells of two tomato genotypes were inoculated with pathogenic and non-pathogenic powdery mildew species, Pseudoidium neolycopersici, Erysiphe trifoliorum and Podosphaera xanthii. On the trichome cells of the tomato cultivar Moneymaker, hyphae of the pathogenic Pseudoidium neolycopersici (isolates KTP-03 and KTP-04) grew vigorously; whereas hyphal growth of the non-pathogenic Erysiphe trifoliorum and Podosphaera xanthii ceased after appressorium formation, which was associated with papilla formation and hypersensitive cell death, respectively. Similar infection processes of the tested powdery mildews were seen in Moneymaker epidermal cells. Therefore, tomato trichomes are suitable for analysing, at individual cell level, the infection processes of different pathotypes of powdery mildews and for observing the cytological responses of plants by non-pathogenic powdery mildews. On the other hand, it was observed that both isolates KTP-03 and KTP-04 failed to produce conidiophores on the hyphae elongating on Moneymaker trichomes. Similarly, no conidiophores were produced on the hyphae elongating on trichomes of Solanum peruvianum LA2172, which is resistant to KTP-03 and susceptible to KTP-04. Interestingly, delayed cell death occurred in LA2172 epidermal cells, which were attacked by KTP-03 hyphae elongating from trichomes and conidiophores were formed on new hyphae growing from the leaf epidermal cells. Thus, leaf trichomes and epidermal cells of the wild tomato species LA2172 reacted differently to the avirulent isolate KTP-03.