Nitrogen nutrition of rice plants under salinity

Two rice (Oryza sativa L.) cultivars, Koshihikari and Pokkali, were grown in solution culture at three concentrations of NaCl or Na₂SO₄ [0 (S0), 50 (S1), and 100 (S2) mmol dm^–3] and three N contents [0.7 (N1), 7 (N2) and 14 (N3) mmol dm^–3]. Salinity significantly decreased dry matter of both cultivars. Pokkali had better growth than Koshihikari under both saline and non-saline conditions. Applications of N enhanced development of shoot dry mass under S0 and S1 treatments up to N2. Under S2, N application had no effect on shoot dry mass of both cultivars. Root dry mass of both cultivars decreased with increasing N application at S1 and S2. Shoot and root NO₃-N content in both rice cultivars increased with increasing N concentration in the nutrient solutions. The absorption of NO₃-N was less in Koshihikari than Pokkali plants, and also was much less in Cl^– than SO₄ ^2– salinity suggesting the antagonism between Cl^– and NO₃ ^–. In addition a significant negative correlation between concentrations of NO₃-N and Cl^– in the shoots or roots was observed in both cultivars     

A quantitative analysis of shear effects on cell suspension and cell culture of perilla frutescens in bioreactors

The short-time effects of shear on suspended cells of Perilla frutescens were quantitatively analyzed by exposing the cells to a well-defined flow field in a rotating drum reactor. It was found that both shear rate and shearing time significantly affected cell viability. The quantitative effects of shear on cell growth and the production of anthocyanin, a secondary metabolite, by the cell cultures were further investigated in a series of batch cultivations using a 5-L plant cell bioreactor with a marine impeller. The results indicated that there was an optimum range of shear rate; i.e., an average shear rate of 20 to 30 s(-1) or an impeller tip speed of 5 to 8 dm/s, which maximized all the values of the following parameters: the specific growth rate, the maximum cell concentration, the (specific) production and productivity of anthocyanin, and the cell and anthocyanin yields. (c) 1994 John Wiley & Sons, Inc.     

Whole‐genome sequencing reveals small genomic regions of introgression in an introduced crater lake population of threespine stickleback

Invasive species pose a major threat to biological diversity. Although introduced populations often experience population bottlenecks, some invasive species are thought to be originated from hybridization between multiple populations or species, which can contribute to the maintenance of high genetic diversity. Recent advances in genome sequencing enable us to trace the evolutionary history of invasive species even at whole‐genome level and may help to identify the history of past hybridization that may be overlooked by traditional marker‐based analysis. Here, we conducted whole‐genome sequencing of eight threespine stickleback (Gasterosteus aculeatus) individuals, four from a recently introduced crater lake population and four of the putative source population. We found that both populations have several small genomic regions with high genetic diversity, which resulted from introgression from a closely related species (Gasterosteus nipponicus). The sizes of the regions were too small to be detected with traditional marker‐based analysis or even some reduced‐representation sequencing methods. Further amplicon sequencing revealed linkage disequilibrium around an introgression site, which suggests the possibility of selective sweep at the introgression site. Thus, interspecies introgression might predate introduction and increase genetic variation in the source population. Whole‐genome sequencing of even a small number of individuals can therefore provide higher resolution inference of history of introduced populations.     

Aggressive encounters between males inChrysolina aurichalcea (Coleoptera: Chrysomelidae)

During the breeding season ofC. aurichalcea, an unpaired male is occasionally seen attacking a mating male on the host plant,Artemisia princeps. To clarify the significance of this behaviour, aggressive encounters between an unpaired male and a mating male were observed 269 times in experimental conditions. Intruders resulted in take-over (10.4%), loss (36.5%), draw (39.0%), or non-interference (14.1%). Frontal attack had 5 times higher probability of take-over than back one. A larger unpaired male had a slightly greater chance of take-over (P<0.02). The importance of aggressive encounters was discussed in view of sperm competition and of cost and benefit.     

Distributions of sensory spots in the hand and two-point discrimination thresholds in the hand, face and mouth in dental students.

Densities of pressure, pain and temperature spots in the back of the hand in 551 students and two-point discrimination thresholds in the hand, the face and the mouth in 684 students were measured. The mean numbers of pressure, pain, warm and cold spots in the back of the hand were 24.7/cm2, 130.5/cm2, 3.4/cm2 and 9.1/cm2, respectively. The mean thresholds of two-point discrimination were 1.7 mm in the tip of the tongue, 2.4 mm in the upper lip, 5.5 mm in the lower jaw, 7.5 mm in the palm, 8.8 mm in the forehead, and 11.8 mm in the back of the hand. There were mostly no differences between males and females in the values of sensory spots and two-point discrimination thresholds.     

Methylnitrosourea induces neural progenitor cell apoptosis and microcephaly in mouse embryos

BACKGROUND: Prenatal exposure to methylnitrosourea (MNU), an alkylating agent, induces microcephaly in mice. However, its pathogenetic mechanism has not been clarified, especially that in the development of the cerebral cortex. METHODS: ICR mice were treated with MNU at 10 mg/kg intraperitoneally on day 13.5 or 15.5 of gestation, and the embryos were observed histologically 24 hr after treatment with MNU or at term. To clarify the pathogenesis of microcephaly and histological changes, especially apoptosis, neurogenesis, and neural migration/positioning, we performed histological analysis employing a cell‐specific labeling experiment using thymidine‐like substances (BrdU, CldU, and IdU) and markers of neurons/neural stem cells. RESULTS: Histological abnormalities of the dorsal telencephalon, and the excessive cell death of proliferative neural progenitor/stem cells were noted in the MNU‐treated embryos. The highest frequencies of cell death occurred at 36 hr after MNU treatment, and little or no neurogenesis was observed in the ventricular zone of the dorsal telencephalon. Abnormality of the radial migration was caused by the reduction of radial fibers in the radial glias. Birth‐date analysis revealed the abnormal positioning of neurons and aberrant lamination of the cerebral cortex. CONCLUSIONS: Our data suggest that prenatal exposure to MNU induces the excessive cell death of neural precursor/stem cells, and the defective development of the cerebral cortex, resulting in microcephalic abnormalities. Birth Defects Res (Part B) 89:213–222, 2010. © 2010 Wiley‐Liss, Inc.     

Antioxidant enzyme responses to salinity stress of Jatropha curcas and J. cinerea at seedling stage

The salt-sensitive humid tropical biodiesel crop, Jatropha curcas, was subjected to a 28-day exposure to salinity (0, 50, 100, and 200 mM NaCl), and activities of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX), the rate of lipid peroxidation, stomatal conductance, mineral contents, and chlorophyll (Chl) content were compared to corresponding characteristics of J. cinerea, a related wild species of saline-dry areas. Biomass production decreased under the influence of 50 mM NaCl in both species, and the reduction was larger in J. curcas than in J. cinerea at the higher NaCl concentrations. In both species, stomatal conductance and transpiration decreased, leaf temperature and Na⁺ concentration increased under salt treatment; salinity effect was stronger in J. curcas. Chl degradation was enhanced only in J. curcas. In both Jatropha species, SOD, CAT, and POX activities increased with salinity. J. curcas showed the higher antioxidant activity than J. cinerea. Lipid peroxidation was observed only in J. curcas at concentrations above 100 mM NaCl, partially due to a greater reduction in stomatal conductance and/or the poor ROS-scavenging system. Thus, J. cinerea had more favorable characteristics to adapt to saline environments, and young J. curcas plants could adapt to salt-affected land if soil salinity was moderate (about 50 mM NaCl in solution).     

Involvement of histidine in complex formation of PriB and single-stranded DNA

PriB is a basic 10-kDa protein that acts as a facilitator in PriA-dependent replication restart in Escherichia coli. PriB has an OB-fold dimer structure and exhibits single-stranded DNA (ssDNA)-binding activities similar to single-stranded binding protein (SSB). In this study, we examined PriB's interaction with ssDNA (oligo-dT35, -dT15, and -dT7) using heteronuclear NMR analysis. Interestingly, ¹H or ¹⁵N chemical shift changes of the PriB main-chain showed two distinct modes using oligo-dT35. The chemical shift perturbation sites in the primary mode were consistent with the main contact site in PriB–ssDNA, which was previously determined by crystal structure analysis. The results also suggested that approximately 8 nt in ssDNA was the main contact site to PriB. In the secondary mode, residues in the α-helix region (His57–Ser65) and in β4–loop3–β5 were mainly perturbed. On the other hand, we examined the state of ssDNA by FRET using 5′-Cy3- and 3′-Cy5-modified oligo-dT35. As the PriB concentration increased, two-step saturation curves were observed in the FRET assay, suggesting a compact structure of ssDNA. Moreover, we confirmed two-step PriB binding to oligo-dT35 using EMSA. The pH dependence of FRET suggested contribution of the His residues. Therefore, we prepared His mutants of PriB and found that His64 in the α-helix region contributed to the second interaction between PriB and ssDNA using FRET and EMSA. Thus, from a structural standpoint, we suggested the role of His64 on the compactness of the PriB–ssDNA complex and on the positive cooperativity of PriB.     

O-glycosylation of protein subpopulations in alcohol-extracted rice proteins

Mucin-type O-glycosylation has been well characterized in mammalian systems but not in plants. In this study, the purified alcohol-soluble, non-reduced protein (prolamin) fraction from rice seed was investigated for the occurrence of O-linked oligosaccharides. As storage prolamins are unlikely to be O-glycosylated, any O-glycosylation found was likely to belong to co-extracted proteins, whether because of association with the protein body or solubility. SDS-PAGE and MS analyses revealed 14 and 16kDa protein families in fractions that bound to the lectins peanut agglutinin (PNA), Vicia villosa lectin (VVL) and Jacalin, indicative of the presence of O-linked saccharides. Enzymatic cleavage, fluorescent labeling and high-performance liquid chromatography (HPLC) analysis demonstrated a peak consistent with Gal-beta-(1-->3)-GalNAc, with similar MS/MS fragmentation. Additionally, upon chemical analysis, a GlcNAc-containing O-linked carbohydrate moiety was discovered. Protein blotting with anti-O-GlcNAc antibody (clone CTD110.6) was positive in a subpopulation of the 14kDa alcohol-soluble protein fraction, but a hot capping experiment was negative. Therefore, the GlcNAc residue in this case is unlikely to be terminal. Additionally, a positive reaction with CTD110.6mAb cannot be taken as absolute proof of O-GlcNAc modification and further confirmatory experiments should be employed. We hypothesize that O-glycosylation may contribute to protein functionality or regulation. Further investigation is required to identify the specific proteins with these modifications. This 'reverse' approach could lead to the identification of proteins involved in mRNA targeting, signaling, translation, anchoring or maintenance of translational quiescence and may be applied to germinating rice seed extracts for further elucidation of protein function and regulation.