A plastidic glucose-6-phosphate dehydrogenase is responsible for hypersensitive response cell death and reactive oxygen species production

Glucose-6-phosphate dehydrogenase (G6PDH) has been implicated in the supply of reduced nicotine amide cofactors for resistance to biotic and abiotic stresses. Here, we show participation of the plastidic P2 isoform of G6PDH in plant immunity. A cytosolic isoform (NbG6PDH-Cyto) and two plastidic isoforms (NbG6PDH-P1 and NbG6PDH-P2) cloned from Nicotiana benthamiana were localized in cytosol and chloroplasts, respectively. Hypersensitive response (HR) cell death and NADPH oxidase (RBOH; respiratory burst oxidase homolog)-dependent reactive oxygen species (ROS) production after recognition of INF1 elicitin, secreted by oomycete Phytophthora infestans, decreased in NbG6PDH-P2-silenced plants, but not in NbG6PDH-Cyto- and NbG6PDH-P1-silenced plants. Silencing of the cytosolic NAD kinase NbNADK1, which phosphorylates NADH to form NADPH, compromised HR cell death and ROS production, and concomitant silencing with NbG6PDH-P2 reduced HR cell death and ROS to levels near those in NbG6PDH-P2-silenced plants. Similarly, silencing NbG6PDH-P2 and NbNADK1 resulted in high susceptibility to P. infestans. These results suggest that NADPH produced by the P2 isoform of G6PDH in chloroplasts is responsible for HR cell death and ROS production mediated by RBOH and that NbNADK1 is involved in this pathway.     

Manipulation of tannins in oaks by galling cynipids

We measured the protein precipitation capacity of tannins in the tissues of Quercus crispula and Quercus serrata galls induced by a cynipid (Trigonaspis sp.) to examine the nutrition hypothesis on gall induction. The protein precipitation capacity was significantly lower in the nutritive tissues of galls, on which the cynipids feed, than in ungalled sound leaves and in the outer gall tissues. In addition, the protein precipitation capacities in the leaves and in the outer gall tissues were significantly larger in Q. crispula than in Q. serrata samples, whereas that of the nutritive tissues did not differ between these oak species. These results suggest that gall induction is one of the adaptations of galling cynipids to host–plant defensive compounds, and support the nutrition hypothesis.     

Long-term effects on tree regeneration of soil scarification with microtopography manipulation in mixed forests of central Hokkaido,northern Japan

Natural regeneration of canopy tree species is generally poor under a selective cutting regime practised in mixed conifer–hardwood stands on Hokkaido, northern Japan, and is prevented by dense bamboo layers in the understory. To promote tree regeneration, we scarified soil in ten sites, with elevations ranging from 420 to 760 m, in 1979, with a rake-equipped bulldozer to produce three different artificial microtopographies (concave, flat, and convex). Twenty-six years after scarification, six canopy tree species (Acer mono, Abies sachalinensis, Betula ermanii, B. maximowicziana, Kalopanax pictus, and Picea jezoensis) had become well established. Abies sachalinensis and B. ermanii regenerated at all sites. Picea jezoensis was well established in high-elevation sites, whereas other hardwood tree species (A. mono, B. maximowicziana, and K. pictus) were well established at low-elevation sites. The Betula species dominated upper layers of regenerated trees, and two conifer species (A. sachalinensis and P. jezoensis) occupied lower layers. Regenerated densities of four (of six) major tree species were positively correlated with standing timber volume of mother trees, whereas those of shade-intolerant species (two Betula species and K. pictus) were negatively correlated with standing timber volume of all canopy trees. Small-seeded species (P. jezoensis and the two Betula species) had higher regeneration densities on convex sites than on other microtopographies. Adequate seed supply, convex substratum for small-seeded species, and control of light conditions for shade-intolerant species should be taken into account when planning regeneration of desirable tree species in central Hokkaido.     

Growth and survival of eel leptocephali (Anguilla japonica) in low-salinity water

We investigated the effects of low-salinity water on the growth, survival, and activity of artificially reared Japanese eel larvae (Anguilla japonica), proceeding from the assumption that such water quality saves energy due to lower cost for osmoregulation. We reared 5-day-old larvae in 0%, 10%, 30%, 50%, 70%, and 100% seawater (SW) with or without diet for 13 days. All larvae reared in 0% and 10% SW died within 6 days, while larvae in 70% and 100% SW survived until 9 days. Larvae in 30% and 50% SW further survived until 13 days without diet. Significant growth in body depth was observed in 30% and 50% SW after 7 days rearing with diet (0.65 ± 0.02 and 0.62 ± 0.02 mm, respectively) as compared with the initial size (0.49 ± 0.03 mm), while no significant growth was observed under the other salinity conditions examined. Larvae swam actively in the light (about 2000 lx) in 50%, 70%, and 100% SW, while they were apparently inactive in 0%, 10%, and 30% SW. The long-term rearing trial showed a 2.2-fold higher 2-month cumulative survival rate in 50% SW (18.2%) than in 100% SW (8.2%). The body depth of larvae in 50% SW (1.58 ± 0.47 mm) was also significantly larger than in 100% SW (1.32 ± 0.35 mm). These findings indicate that the intermediate salinity can result in better growth and survival performance in Japanese eel larvae.     

Acoustic pressure sensitivities and effects of particle motion in red sea bream Pagrus major

The auditory pressure thresholds of red sea bream were examined using cardiac response in the field by placing fish subjects far from the sound source to prevent particle motion. Pressure and particle motion thresholds were also obtained using the auditory brainstem response (ABR) technique. The thresholds at 100 and 200 Hz were significantly higher when measured using the cardiac response in the far field than those obtained in previously conducted experiments in experimental tub. However, thresholds obtained using ABR from 200 to 500 Hz were not remarkably lower, although significantly different (0.01 < P < 0.05), compared with those obtained using cardiac response in the far field. Furthermore, calculated particle velocity thresholds indicated that fish probably detected particle motion within the frequency range of 50–200 Hz, even in fish with a deactivated lateral line. Although the ABR method is widely applied in fish auditory study, hearing thresholds are apparently affected by particle motion.     

Effect of temperature decrease on oocyte development,sex steroids,and gonadotropin β-subunit mRNA expression levels in female Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis>

To improve understanding of the mechanism of early ovarian development in eels, the effects of water temperature decrease on oocyte development, plasma levels of sex steroids [estradiol 17β (E2), testosterone (T), 11-ketotestosterone (11-KT)], and gonadotropin β-subunit [follicle-stimulating hormone (FSHβ), luteinizing hormone (LHβ)] messenger RNA (mRNA) expression levels were investigated. A total of 27 female Japanese eels Anguilla japonica were divided into initial, control, and test (water temperature decrease) groups. Starting on 22 September 2009, eels in the test group were reared in a tank with gradual temperature decrease from 25°C to 15°C over 39 days, while the control group was maintained at 25°C. The test group accumulated more oil droplets in their oocytes than did the other groups. Levels of sex steroids, especially 11-KT, were higher in the test group. In contrast, FSHβ and LHβ mRNA expression levels were lower in the test group. These results suggest that water temperature decrease only induced an early stage of ovarian development that was partly affected by an 11-KT increase. For further maturation, other environmental factors related to induction of gonadotropin increase appear to be needed.     

Evaluation of S100B in cerebrospinal fluid as a potential biomarker for neurological diseases in calves

S100B in cerebrospinal fluid (CSF-S100B) was measured in calves with 20 neurologic and 21 non-neurologic diseases to clarify its utility as a biomarker for neurologic diseases. The median CSF-S100B value in the neurologic disease group (43.0 ng/ml) was significantly higher than that in the non-neurologic disease group (10.2 ng/ml). As CSF-S100B levels in calves with neurologic diseases widely differed, the utility of CSF-S100B as a diagnostic marker for neurologic diseases in cattle remains inconclusive.     

Involvement of nitric oxide generation in hypersensitive cell death induced by elicitin in tobacco cell suspension culture

Recent studies suggest that nitric oxide (NO), an important signaling and defense molecule in mammals, plays a key role in activating disease resistance in plants. We characterized NO production by tobacco Bright Yellow-2 cells pharmacologically after treatment with INF1, the major elicitin secreted by the late blight pathogen Phytophthora infestans, prepared from Escherichia coli. NO production rapidly occurred within 1h and reached a maximum level 3–6h after the addition of INF1. Carboxy-PTIO, a NO-specific scavenger, abolished INF1-induced NO production in a dose-dependent manner. Pretreatment of protein synthesis inhibitor cycloheximide and protein kinase inhibitor K252a blocked NO production 3–12h after INF1 treatment, indicating that NO production requires de novo protein synthesis and protein phosphorylation. In an investigation of the relations between NO generation and several defense responses induced by INF1, carboxy-PTIO completely suppressed activation of a 41-kDa protein kinase and cell death by INF1. Carboxy-PTIO also suppressed the induction of hypersensitive-related (hsr) genes HSR515 and HSR203J, the expression of which is strongly correlated with the hypersensitive response in plants. The results suggest that NO plays a crucial role in the induction of hypersensitive cell death.     

Long-term outcome of myotonia associated with hyperadrenocorticism in 2 dogs

Two dogs were diagnosed with myotonia associated with hyperadrenocorticism and treated with trilostane. One dog showed temporary improvement, but the other dog showed no improvement. The dogs survived 2383 and 1902 days, respectively. Findings suggest that myotonia persists despite treatment, but this condition is not associated with a poor prognosis for survival.