Genetic and Physiological Characterization of Soybean-Nodule-Derived Isolates from Bangladeshi Soils Revealed Diverse Array of Bacteria with Potential Bradyrhizobia for Biofertilizers

Genetic and physiological characterization of bacteria derived from nodules of leguminous plants in the exploration of biofertilizer is of paramount importance from agricultural and environmental perspectives. Phylogenetic analysis of the 16S rRNA gene of 84 isolates derived from Bangladeshi soils revealed an unpredictably diverse array of nodule-forming and endosymbiotic bacteria-mostly belonging to the genus Bradyrhizobium. A sequence analysis of the symbiotic genes (nifH and nodD1) revealed similarities with the 16S rRNA gene tree, with few discrepancies. A phylogenetic analysis of the partial rrn operon (16S-ITS-23S) and multi-locus sequence analysis of atpD, glnII, and gyrB identified that the Bradyrhizobium isolates belonged to Bradyrhizobium diazoefficiens, Bradyrhizobium elkanii, Bradyrhizobium liaoningense and Bradyrhizobium yuanmingense species. In the pot experiment, several isolates showed better activity than B. diazoefficiens USDA110, and the Bho-P2-B2-S1-51 isolate of B. liaoningense showed significantly higher acetylene reduction activity in both Glycine max cv. Enrei and Binasoybean-3 varieties and biomass production increased by 9% in the Binasoybean-3 variety. Tha-P2-B1-S1-68 isolate of B. diazoefficiens significantly enhanced shoot length and induced 10% biomass production in Binasoybean-3. These isolates grew at 1-4% NaCl concentration and pH 4.5-10 and survived at 45 °C, making the isolates potential candidates for eco-friendly soybean biofertilizers in salty and tropical regions.

Plant Growth-promoting Effects of Viable and Dead Spores of Bacillus pumilus TUAT1 on Setaria viridis

Spores are a stress-resistant form of Bacillus spp., which include species that are plant growth-promoting rhizobacteria (PGPR). Previous studies showed that the inoculation of plants with vegetative cells or spores exerted different plant growth-promoting effects. To elucidate the spore-specific mechanism, we compared the effects of viable vegetative cells, autoclaved dead spores, and viable spores of Bacillus pumilus TUAT1 inoculated at 10⁷ CFU plant^–1 on the growth of the C4 model plant, Setaria viridis A10.1. B. pumilus TUAT1 spores exerted stronger growth-promoting effects on Setaria than on control plants 14 days after the inoculation. Viable spores increased shoot weight, root weight, shoot length, root length, and nitrogen uptake efficiency 21 days after the inoculation. These increases involved primary and crown root formation. Additionally, autoclaved dead spores inoculated at 10⁸ or 10⁹ CFU plant^–1 had a positive impact on crown root differentiation, which increased total lateral root length, resulting in a greater biomass and more efficient nitrogen uptake. The present results indicate that an inoculation with viable spores of B. pumilus TUAT1 is more effective at enhancing the growth of Setaria than that with vegetative cells. The plant response to dead spores suggests that the spore-specific plant growth-promoting mechanism is at least partly independent of symbiotic colonization.

Isolation and Characterization of Phosphate Solubilizing Bacteria from Paddy Field Soils in Japan

Phosphorus (P) is abundant in soil and is essential for plant growth and development; however, it is easily rendered insoluble in complexes of different types of phosphates, which may lead to P deficiency. Therefore, increases in the amount of P released from phosphate minerals using microbial inoculants is an important aspect of agriculture. The present study used inorganic phosphate solubilizing bacteria (iPSB) in paddy field soils to develop microbial inoculants. Soils planted with rice were collected from different regions of Japan. Soil P was sequentially fractionated using the Hedley method. iPSB were isolated using selective media supplemented with tricalcium phosphate (Ca-P), aluminum phosphate (Al-P), or iron phosphate (Fe-P). Representative isolates were selected based on the P solubilization index and soil sampling site. Identification was performed using 16S rRNA and rpoB gene sequencing. Effectiveness was screened based on rice cultivar Koshihikari growth supplemented with Ca-P, Al-P, or Fe-P as the sole P source. Despite the relatively homogenous soil pH of paddy field sources, three sets of iPSB were isolated, suggesting the influence of fertilizer management and soil types. Most isolates were categorized as β-Proteobacteria (43%). To the best of our knowledge, this is the first study to describe the genera Pleomorphomonas, Rhodanobacter, and Trinickia as iPSB. Acidovorax sp. JC5, Pseudomonas sp. JC11, Burkholderia sp. JA6 and JA10, Sphingomonas sp. JA11, Mycolicibacterium sp. JF5, and Variovorax sp. JF6 promoted plant growth in rice supplemented with an insoluble P source. The iPSBs obtained may be developed as microbial inoculants for various soil types with different P fixation capacities.

Genetic Diversity and Characterization of Symbiotic Bacteria Isolated from Endemic Phaseolus Cultivars Located in Contrasting Agroecosystems in Venezuela

Phaseolus vulgaris is a grain cultivated in vast areas of different countries. It is an excellent alternative to the other legumes in the Venezuelan diet and is of great agronomic interest due to its resistance to soil acidity, drought, and high temperatures. Phaseolus establishes symbiosis primarily with Rhizobium and Ensifer species in most countries, and this rhizobia-legume interaction has been studied in Asia, Africa, and the Americas. However, there is currently no evidence to show that rhizobia nodulate the endemic cultivars of P. vulgaris in Venezuela. Therefore, we herein investigated the phylogenetic diversity of plant growth-promoting and N2-fixing nodulating bacteria isolated from the root nodules of P. vulgaris cultivars in a different agroecosystem in Venezuela. In comparisons with other countries, higher diversity was found in isolates from P. vulgaris nodules, ranging from α- and β-proteobacteria. Some isolates belonging to several new phylogenetic lineages within Bradyrhizobium, Ensifer, and Mesorhizobium species were also specifically isolated at some topographical regions. Additionally, some isolates exhibited tolerance to high temperature, acidity, alkaline pH, salinity stress, and high Al levels; some of these characteristics may be related to the origin of the isolates. Some isolates showed high tolerance to Al toxicity as well as strong plant growth-promoting and antifungal activities, thereby providing a promising agricultural resource for inoculating crops.

Isolation and Screening of Indigenous Plant Growth-promoting Rhizobacteria from Different Rice Cultivars in Afghanistan Soils

To develop biofertilizers for rice in Afghanistan, 98 plant growth-promoting rhizobacteria were isolated from rice plants and their morphological and physiological characteristics, such as indole-3-acetic acid production, acetylene reduction, phosphate and potassium solubilization, and siderophore production, were evaluated. The genetic diversity of these bacteria was also analyzed based on 16S rRNA gene sequences. Of 98 bacteria, 89.7% produced IAA, 54.0% exhibited nitrogenase activity, and 40% showed phosphate solubilization and siderophore production. Some isolates assigned to Pseudomonas (brassicacearum, chengduensis, plecoglossicida, resinovorans, and straminea) formed a relationship with rice, and P. resinovorans and P. straminea showed nitrogen fixation. Rhizobium borbori and R. rosettiformans showed a relationship with rice plants and nitrogen fixation. Among the isolates examined, AF134 and AF137 belonging to Enterobacter ludwigii and P. putida produced large amounts of IAA (92.3 μg mL⁻¹) and exhibited high nitrogenase activity (647.4 nmol C₂H₄ h⁻¹), respectively. In the plant growth test, more than 70% of the inoculated isolates showed significantly increased root and shoot dry weights. Highly diverse bacterial isolates showing promising rice growth-promoting traits were obtained from Afghanistan alkaline soils.

Phloem-specific overexpression of AtOPT6 in Arabidopsis enhances Zn transport into shoots

The Arabidopsis oligopeptide transporter AtOPT6 is membrane transport protein that mediated transport of glutathione in both the reduced (GSH) and oxidized (GSSG) forms. In this study, the role of AtOPT6 in glutathione distribution throughout the plant was investigated. We found that transgenic Arabidopsis overexpressing AtOPT6 under the control of a phloem-specific promoter of sucrose-proton symporter 2 (pSUC2), remarkably increased AtOPT6 transcript levels, ranging from 30- to 40-fold in shoots and 6- to 10-fold in roots, relative to the wild type. AtOPT6-overexpressing lines could elevate the foliar glutathione content; however, glutathione content in the phloem did not change. We observed that the ratio of shoot glutathione content to total glutathione content increased in AtOPT6-overexpressing lines, but not in transgenic Arabidopsis with elevated foliar GSH synthesis. These results indicate the possibility that loading and unloading of glutathione in phloem tissues are enhanced in AtOPT6-overexpressing lines under the control of pSUC2. The results of heavy metal analysis revealed that transgenic Arabidopsis overexpressing AtOPT6 under the control of pSUC2 could promote the transport of Zn into shoots as effectively as transgenic Arabidopsis with elevated foliar GSH synthesis, or wild-type plants with exogenous foliar application of GSH.

Elevated glutathione synthesis in leaves contributes to zinc transport from roots to shoots in Arabidopsis

Glutathione (GSH) is a vital compound involved in several plant metabolic pathways. Our previous study indicated that foliar GSH application can increase zinc (Zn) levels in leafy vegetables. The objective of this study was to determine the mode of action of GSH as it relates to Zn transport from roots to shoots. Two types of transgenic Arabidopsis plants with genes for GSH synthesis, including StGCS-GS or AtGSH1 driven by the leaf-specific promoter of chlorophyll a/b-binding protein (pCab3) gene were generated. Both types of transgenic Arabidopsis plants showed significant increases in shoot GSH concentrations compared to the wild type (WT). Monitoring ⁶⁵Zn movement by positron-emitting tracer imaging system (PETIS) analysis indicated that the ⁶⁵Zn amount in the shoots of both types of transgenic Arabidopsis plants were higher than that in the WT. GSH concentration in phloem sap was increased significantly in WT with foliar applications of 10 mM GSH (WT-GSH), but not in transgenic Arabidopsis with elevated foliar GSH synthesis. Both types of transgenic Arabidopsis with elevated foliar GSH synthesis and WT-GSH exhibited increased shoot Zn concentrations and Zn translocation ratios. These results suggest that enhancement of endogenous foliar GSH synthesis and exogenous foliar GSH application affect root-to-shoot transport of Zn.

Evaluation of Immune Responses Induced by Simultaneous Inoculations of Soybean (Glycine max [L.] Merr.) with Soil Bacteria and Rhizobia

Legumes form root nodules and fix atmospheric nitrogen by establishing symbiosis with rhizobia. However, excessive root nodules are harmful to plants because of the resulting overconsumption of energy from photosynthates. The delay of an inoculation of the soybean super-nodulation mutant NOD1-3 with Bradyrhizobium diazoefficiens USDA110T by 5 d after an inoculation with several soil bacteria confirmed that one bacterial group significantly decreased root nodules throughout the study period. Moreover, no significant changes were observed in nitrogen fixation by root nodules between an inoculation with USDA 110T only and co-inoculation treatments. To clarify the potential involvement of PR proteins in the restriction of nodule formation in the plants tested, the relative expression levels of PR-1, PR-2, PR-5, and PDF1.2 in NOD1-3 roots were measured using real-time PCR. One group of soil bacteria (Gr.3), which markedly reduced nodule numbers, significantly induced the expression of PR-1, PR-5 and PDF1.2 genes by day 5 after the inoculation. By days 7, 10, and 20 after the inoculation, the expression levels of PR-2 and PR-5 were lower than those with the uninoculated treatment. Inoculations with this group of soil bacteria resulted in lower root nodule numbers than with other tested soil bacteria exerting weak inhibitory effects on nodulation, and were accompanied by the induction of plant defense-related genes. Thus, PR genes appear to play important roles in the mechanisms that suppresses nodule formation on soybean roots.

Burkholderia and Paraburkholderia are Predominant Soybean Rhizobial Genera in Venezuelan Soils in Different Climatic and Topographical Regions

The climate, topography, fauna, and flora of Venezuela are highly diverse. However, limited information is currently available on the characterization of soybean rhizobia in Venezuela. To clarify the physiological and genetic diversities of soybean rhizobia in Venezuela, soybean root nodules were collected from 11 soil types located in different topographical regions. A total of 395 root nodules were collected and 120 isolates were obtained. All isolates were classified in terms of stress tolerance under different concentrations of NaCl and Al3+. The tolerance levels of isolates to NaCl and Al3+ varied. Based on sampling origins and stress tolerance levels, 44 isolates were selected for further characterization. An inoculation test indicated that all isolates showed the capacity for root nodulation on soybean. Based on multilocus sequence typing (MLST), 20 isolates were classified into the genera Rhizobium and Bradyrhizobium. The remaining 24 isolates were classified into the genus Burkholderia or Paraburkholderia. There is currently no evidence to demonstrate that the genera Burkholderia and Paraburkholderia are the predominant soybean rhizobia in agricultural fields. Of the 24 isolates classified in (Para) Burkholderia, the nodD-nodB intergenic spacer regions of 10 isolates and the nifH gene sequences of 17 isolates were closely related to the genera Rhizobium and Bradyrhizobium, respectively. The root nodulation numbers of five (Para) Burkholderia isolates were higher than those of the 20 α-rhizobia. Furthermore, among the 44 isolates tested, one Paraburkholderia isolate exhibited the highest nitrogen-fixation activity in root nodules.

AtOPT6 Protein Functions in Long-Distance Transport of Glutathione in Arabidopsis thaliana

The involvement of the Arabidopsis oligopeptide transporter AtOPT6, which was previously shown to take up glutathione (GSH) when expressed in yeast cells or in Xenopus laevis oocytes, in GSH transport was analyzed using opt6 knockout mutant lines. The concentration of GSH in flowers or siliques was lower in opt6 mutants relative to wild-type plants, suggesting involvement of AtOPT6 in long-distance transport of GSH. The GSH concentration in phloem sap was similar between opt6 mutants and wild-type plants. These results, combined with earlier reports showing expression of AtOPT6 in the vascular bundle, especially in the cambial zone, suggest that AtOPT6 functions to transport GSH into cells surrounding the phloem in sink organs. The opt6 mutant plants showed delayed bolting, implying the importance of AtOPT6 for regulation of the transition from vegetative to reproductive growth. After cadmium (Cd) treatment, the concentration of the major phytochelatin PC2 was lower in flowers in the opt6 mutants and Cd was accumulated in roots of opt6 mutant plants compared with wild-type plants. These results suggest that AtOPT6 is likely to be involved in transporting GSH, PCs and Cd complexed with these thiols into sink organs.

Visualization of zinc dynamics in intact plants using positron imaging of commercially available 65Zn

BACKGROUND

Positron imaging can be used to non-destructively visualize the dynamics of a positron-emitting radionuclide in vivo, and is therefore a tool for understanding the mechanisms of nutrient transport in intact plants. The transport of zinc, which is one of the most important nutrient elements for plants, has so far been visualized by positron imaging using ⁶²Zn (half-life: 9.2 h), which is manufactured in the limited number of facilities that have a cyclotron. In contrast, the positron-emitting radionuclide ⁶⁵Zn (half-life: 244 days) is commercially available worldwide. In this study, we examined the possibility of conducting positron imaging of zinc in intact plants using ⁶⁵Zn.

RESULTS

By administering ⁶⁵Zn and imaging over a long time, clear serial images of ⁶⁵Zn distributions from the root to the panicle of dwarf rice plants were successfully obtained.

CONCLUSIONS

Non-destructive visualization of zinc dynamics in plants was achieved using commercially available ⁶⁵Zn and a positron imaging system, demonstrating that zinc dynamics can be visualized even in facilities without a cyclotron.

Genetic Characterization of Soybean Rhizobia Isolated from Different Ecological Zones in North-Eastern Afghanistan

Seventy rhizobial isolates were obtained from the root nodules of two soybean (Glycine max) cultivars: Japanese cultivar Enrei and USA cultivar Stine3300, which were inoculated with different soil samples from Afghanistan. In order to study the genetic properties of the isolates, the DNA sequences of the 16S rRNA gene and symbiotic genes (nodD1 and nifD) were elucidated. Furthermore, the isolates were inoculated into the roots of two soybean cultivars, and root nodule numbers and nitrogen fixation abilities were subsequently evaluated in order to assess symbiotic performance. Based on 16S rRNA gene sequences, the Afghanistan isolates obtained from soybean root nodules were classified into two genera, Bradyrhizobium and Ensifer. Bradyrhizobium isolates accounted for 54.3% (38) of the isolates, and these isolates had a close relationship with Bradyrhizobium liaoningense and B. yuanmingense. Five out of the 38 Bradyrhizobium isolates showed a novel lineage for B. liaoningense and B. yuanmingense. Thirty-two out of the 70 isolates were identified as Ensifer fredii. An Ensifer isolate had identical nodD1 and nifD sequences to those in B. yuanmingense. This result indicated that the horizontal gene transfer of symbiotic genes occurred from Bradyrhizobium to Ensifer in Afghanistan soil. The symbiotic performance of the 14 tested isolates from the root nodules of the two soybean cultivars indicated that Bradyrhizobium isolates exhibited stronger acetylene reduction activities than Ensifer isolates. This is the first study to genetically characterize soybean-nodulating rhizobia in Afghanistan soil.

Temporal changes of radiocesium in irrigated paddy fields and its accumulation in rice plants in Fukushima

About half of the total paddy field area, which is the dominant agricultural land in Fukushima Prefecture, was contaminated by radiocesium released by the Fukushima Daiichi Nuclear Power Plant accident. In this study, we investigated the temporal changes of radiocesium in soil, irrigation water, and rice plant in two adjacent rice paddies, with and without surface-soil-removal, in Fukushima Prefecture for over three years (2012-2014) after the nuclear accident. Our results showed that radiocesium migrated into 24-28 cm soil layers and that the activity concentration of radiocesium in paddy soils showed a significant reduction in 2014. The newly added radiocesium to paddies through irrigation water contributed only a maximum value of 0.15% and 0.75% of the total amount present in control and decontaminated paddies, respectively, throughout the study period. The radiocesium activity concentration in suspended sediment in irrigation water exponentially decreased, and the effective half-lives (Teff) for (137)Cs and (134)Cs were 1.3 and 0.9 years, respectively. Additionally, the average suspended sediment concentration in irrigation water increased between 2012 and 2014, suggesting that enhanced soil erosion had occurred in the surrounding environment. Radiocesium accumulation in rice plant also decreased with time in both paddies. However, the concentration ratio of radiocesium for rice plant in the decontaminated paddy increased compared with control paddy, despite approximately 96% of fallout radiocesium removed in paddy soil. Further analysis is required to clarify the reasons of high concentration ratio of radiocesium for rice plant in the decontaminated paddy.

Growth and (137)Cs uptake of four Brassica species influenced by inoculation with a plant growth-promoting rhizobacterium Bacillus pumilus in three contaminated farmlands in Fukushima prefecture, Japan

The effectiveness of the plant growth-promoting rhizobacterium Bacillus pumilus regarding growth promotion and radiocesium ((137)Cs) uptake was evaluated in four Brassica species grown on different (137)Cs contaminated farmlands at Fukushima prefecture in Japan from June to August 2012. B. pumilus inoculation did not enhance growth in any of the plants, although it resulted in a significant increase of (137)Cs concentration and higher (137)Cs transfer from the soil to plants. The Brassica species exhibited different (137)Cs uptake abilities in the order Komatsuna>turnip>mustard>radish. TF values of (137)Cs ranged from 0.018 to 0.069 for all vegetables. Komatsuna possessed the largest root surface area and root volume, and showed a higher (137)Cs concentration in plant tissue and higher (137)Cs TF values (0.060) than the other vegetables. Higher (137)Cs transfer to plants was prominent in soil with a high amount of organic matter and an Al-vermiculite clay mineral type.

Higher sterol content regulated by CYP51 with concomitant lower phospholipid content in membranes is a common strategy for aluminium tolerance in several plant species

Several studies have shown that differences in lipid composition and in the lipid biosynthetic pathway affect the aluminium (Al) tolerance of plants, but little is known about the molecular mechanisms underlying these differences. Phospholipids create a negative charge at the surface of the plasma membrane and enhance Al sensitivity as a result of the accumulation of positively charged Al(3+) ions. The phospholipids will be balanced by other electrically neutral lipids, such as sterols. In the present research, Al tolerance was compared among pea (Pisum sativum) genotypes. Compared with Al-tolerant genotypes, the Al-sensitive genotype accumulated more Al in the root tip, had a less intact plasma membrane, and showed a lower expression level of PsCYP51, which encodes obtusifoliol-14α-demethylase (OBT 14DM), a key sterol biosynthetic enzyme. The ratio of phospholipids to sterols was higher in the sensitive genotype than in the tolerant genotypes, suggesting that the sterol biosynthetic pathway plays an important role in Al tolerance. Consistent with this idea, a transgenic Arabidopsis thaliana line with knocked-down AtCYP51 expression showed an Al-sensitive phenotype. Uniconazole-P, an inhibitor of OBT 14DM, suppressed the Al tolerance of Al-tolerant genotypes of maize (Zea mays), sorghum (Sorghum bicolor), rice (Oryza sativa), wheat (Triticum aestivum), and triticale (×Triticosecale Wittmark cv. Currency). These results suggest that increased sterol content, regulated by CYP51, with concomitant lower phospholipid content in the root tip, results in lower negativity of the plasma membrane. This appears to be a common strategy for Al tolerance among several plant species.

Radioactive pollution and accumulation of radionuclides in wild plants in Fukushima

The radionuclide status of wild plants and soil in the Fukushima area was investigated during the period May 2011 to October 2012, using an imaging plate (autoradiograms) or a high purity germanium detector. Analyses of autoradiograms showed that wild plants grown in March 2011 were strongly polluted with fallout released from the Fukushima 1 Nuclear Power Plant. The radioactivity was mostly due to fallout adsorbed on the surface of the plants. On the other hand, a number of herbaceous plants were regularly collected in the Fukushima area and their radionuclide concentrations were measured with a high-purity germanium detector. Plants grown in March 2011 showed very high levels of ¹³⁴Cs and ¹³⁷Cs, but these radioactivity levels decreased rapidly after July 2011 and eventually became lower than that of endogenous ⁴⁰K. During this period, the radioactivity of the soil remained high. We therefore suppose that a significant proportion of the radioactivity detected from plants harvested after July 2011 was most likely derived from soil dust attached on the plant surface. Autoradiograms of rice plants were virtually identical between plants cultivated in Fukushima and Osaka area, reflecting the background radiation due to ⁴⁰K.

Evaluation of the radioactive Cs concentration in brown rice based on the K nutritional status of shoots

The radioactive cesium ((134,137)Cs) concentration in brown rice is correlated with that in the straw/husk. The distribution of (134,137)Cs, resembles that of potassium (K), a homologous element of Cs, in the rice plant body. The relative isotopic abundance of (40)K is 0.0117 %; thus, 1 g K contains 30.4 Bq ⁴⁰K, and the mass of 4,000 Bq (40)K is 0.0154 g, indicating that the K concentration can be calculated from (40)K concentration. We examined if the radioactive Cs concentration in brown rice can be estimated from (40)K concentrations in straw, and especially might be predicted from the (40)K:(134,137)Cs ratio in straw. We determined the concentrations of (40)K and radioactive Cs in straw and brown rice, and found a strong correlated-equation (y = 72.922 x(-0.759); r = 0.907) between the radioactive Cs concentration in brown rice and the ⁴⁰K:(134,137)Cs ratio in straw. The estimated-radioactive Cs concentration in brown rice can be as much as double, depending on the K nutritional status changing the ⁴⁰K:(134,137)Cs ratio in straw. We herein propose a nutritional diagnosis that radioactive Cs concentrations in brown rice can be predicted from the ⁴⁰K:(134,137)Cs ratio in shoots.

Rice (Oryza sativa L.) roots have iodate reduction activity in response to iodine

Although iodine is not an essential nutrient for higher plants, their roots take up and transport the element. However, the exact mechanisms involved in iodine uptake and metabolism in higher plants have yet to be elucidated. In this study, we compared two cultivars differing in iodine tolerance ("Nipponbare" and "Gohyakumangoku") to increasing levels of I(-) and IO(-) 3 in the root solutions of water-cultured rice (Oryza sativa L.). We found that IO(-) 3 added to the root solutions was converted to I(-) in the presence of roots. Iodate reduction occurred over the course of several hours. Furthermore, the iodate reduction activity of "Nipponbare" (iodine-sensitive) and "Gohyakumangoku" (iodine-tolerant) roots increased after adding IO(-) 3 or I(-). The roots of barley and soybean also showed iodate reduction activity and the activity responded to iodine treatment either with IO(-) 3 and I(-). This study suggests that plant roots biologically reduce iodate to iodide and indicates that the iodate reduction activity of roots responds to external iodine conditions.

How do nitrogen and phosphorus deficiencies affect strigolactone production and exudation?

Plants exude strigolactones (SLs) to attract symbiotic arbuscular mycorrhizal fungi in the rhizosphere. Previous studies have demonstrated that phosphorus (P) deficiency, but not nitrogen (N) deficiency, significantly promotes SL exudation in red clover, while in sorghum not only P deficiency but also N deficiency enhances SL exudation. There are differences between plant species in SL exudation under P- and N-deficient conditions, which may possibly be related to differences between legumes and non-legumes. To investigate this possibility in detail, the effects of N and P deficiencies on SL exudation were examined in Fabaceae (alfalfa and Chinese milk vetch), Asteraceae (marigold and lettuce), Solanaceae (tomato), and Poaceae (wheat) plants. In alfalfa as expected, and unexpectedly in tomato, only P deficiency promoted SL exudation. In contrast, in Chinese milk vetch, a leguminous plant, and in the other non-leguminous plants examined, N deficiency as well as P deficiency enhanced SL exudation. Distinct reductions in shoot P levels were observed in plants grown under N deficiency, except for tomato, in which shoot P level was increased by N starvation, suggesting that the P status of the shoot regulates SL exudation. There seems to be a correlation between shoot P levels and SL exudation across the species/families investigated.

How do nitrogen and phosphorus deficiencies affect strigolactone production and exudation?

Plants exude strigolactones (SLs) to attract symbiotic arbuscular mycorrhizal fungi in the rhizosphere. Previous studies have demonstrated that phosphorus (P) deficiency, but not nitrogen (N) deficiency, significantly promotes SL exudation in red clover, while in sorghum not only P deficiency but also N deficiency enhances SL exudation. There are differences between plant species in SL exudation under P- and N-deficient conditions, which may possibly be related to differences between legumes and non-legumes. To investigate this possibility in detail, the effects of N and P deficiencies on SL exudation were examined in Fabaceae (alfalfa and Chinese milk vetch), Asteraceae (marigold and lettuce), Solanaceae (tomato), and Poaceae (wheat) plants. In alfalfa as expected, and unexpectedly in tomato, only P deficiency promoted SL exudation. In contrast, in Chinese milk vetch, a leguminous plant, and in the other non-leguminous plants examined, N deficiency as well as P deficiency enhanced SL exudation. Distinct reductions in shoot P levels were observed in plants grown under N deficiency, except for tomato, in which shoot P level was increased by N starvation, suggesting that the P status of the shoot regulates SL exudation. There seems to be a correlation between shoot P levels and SL exudation across the species/families investigated.

Phenotypic and genetic characterization of rhizobia associated with alfalfa in the Hokkaido and Ishigaki regions of Japan

Twenty five rhizobial isolates were obtained from root nodules of Medicago sativa inoculated with soil samples collected from the Sapporo region and Ishigaki Island in Japan. To study their diversity and characterize them in relation to the climatic conditions of their soils of origin, a polyphasic approach analyzing stress tolerance, symbiotic and genetic properties was used. Stress tolerance assays revealed marked variations in salinity, pH and temperature tolerance. Isolates originating from a sub-tropical climate in alkaline soil (Ishigaki Island) tolerated high temperature, salinity and pH levels. Moreover, isolates recovered from a temperate climate in acidic soil (Sapporo) were sensitive to high temperature and salinity, and tolerated acidic pH. Phylogenetic analysis of conserved 16S rRNA and recA genes, and symbiotic nodA and nifDK revealed 25 isolates to be closely related to Ensifer meliloti. Furthermore, the branch patterns of phylogenetic trees constructed from different genes revealed the existence of at least two E. meliloti types in the soils studied. These results may be relevant to programs directed towards improving crop productivity through biofertilization with locally adapted and genetically defined strains.

Phylogenetic diversity and symbiotic functioning in mungbean (Vigna radiata L. Wilczek) bradyrhizobia from contrast agro-ecological regions of Nepal

Nepal consists wide range of climatic and topographical variations. Here, we explored the phylogeny of native mungbean bradyrhizobia isolated from different agro-ecological regions of Nepal and accessed their nodulation and nitrogen fixation characteristics. Soil samples were collected from three agro-ecological regions with contrasting climate and topography. A local mungbean cultivar, Kalyan, was used as a trap plant. We characterized isolates based on the full nucleotide sequence of the 16S rRNA, ITS region, and nodA genes; and partial sequences of nodD1 and nifD genes. We found 50% of isolates phylogenetically related to B. yuanmingense, 13% to B. japonicum, 8% to B. elkanii, and 29% to novel phylogenetic origin. Results of the inoculation test suggested that expression of different symbiotic genes in isolates resulted in different degrees of symbiotic functioning. Our results indicate B. yuanmingense and novel strains are more efficient symbiotic partners than B. elkanii for the local mungbean cv. Kalyan. We also found most mungbean rhizobial genotypes were conserved across agro-ecological regions. All the strains from tropical Terai region belonged to B. yuanmingense or a novel lineage of B. yuanmingense, and dominance of B. japonicum related strains was observed in the Hill region. Higher genetic diversity of Bradyrhizobium strains was observed in temperate and sub-tropical region than in the tropical region.

Stress tolerance and symbiotic and phylogenic features of root nodule bacteria associated with Medicago species in different bioclimatic regions of Tunisia

Thirty two rhizobial isolates were obtained from different bioclimatic regions of Tunisia using as trap plants, Medicago sativa, Medicago ciliaris, Medicago polymorpha and Medicago minima. To study their diversity and characterize them in relation to Mediterranean conditions, abiotic stress resistance, symbiotic properties and genetic diversity in terms of 16S rRNA and nodA sequences were assessed. Five isolates from M. sativa, three from M. ciliaris and three from M. minima could grow at 45°C. Only two isolates from M. sativa grew at 4% NaCl. The most stress tolerant isolates were obtained from arid soils. A phylogenetic analysis of 16S rRNA genes revealed 29 isolates to be closely related to Ensifer including one (Pl.3-9) that showed a 16S rRNA sequence similar to that of Ensifer meliloti and nodA sequence similar to that of Ensifer medicae. However, three isolates were categorized into Agrobacterium containing the nodA of Ensifer. Furthermore, these isolates developed nodules on original hosts. The results for the four isolates suggest horizontal gene transfer between the species.

Genetic diversity of native soybean bradyrhizobia from different topographical regions along the southern slopes of the Himalayan Mountains in Nepal

Soybean-nodulating bradyrhizobia are genetically diverse and are classified into different species. In this study, the genetic diversity of native soybean bradyrhizobia isolated from different topographical regions along the southern slopes of the Himalayan Mountains in Nepal was explored. Soil samples were collected from three different topographical regions with contrasting climates. A local soybean cultivar, Cobb, was used as a trap plant to isolate bradyrhizobia. A total of 24 isolates selected on the basis of their colony morphology were genetically characterized. For each isolate, the full nucleotide sequence of the 16S rRNA gene and ITS region, and partial sequences of the nifD and nodD1 genes were determined. Two lineages were evident in the conserved gene phylogeny; one representing Bradyrhizobium elkanii (71% of isolates), and the other representing Bradyrhizobium japonicum (21%) and Bradyrhizobium yuanmingense (8%). Phylogenetic analyses revealed three novel lineages in the Bradyrhizobium elkanii clade, indicating high levels of genetic diversity among Bradyrhizobium isolates in Nepal. B. japonicum and B. yuanmingense strains were distributed in areas from 2420 to 2660 m above sea level (asl), which were mountain regions with a temperate climate. The B. elkanii clade was distributed in two regions; hill regions ranging from 1512 to 1935 m asl, and mountain regions ranging from 2420 to 2660 m asl. Ten multi-locus genotypes were detected; seven among B. elkanii, two among B. japonicum, and one among B. yuanmingense-related isolates. The results indicated that there was higher species-level diversity of Bradyrhizobium in the temperate region than in the sub-tropical region along the southern slopes of the Himalayan Mountains in Nepal.

BRASSINOSTEROID UPREGULATED1, encoding a helix-loop-helix protein, is a novel gene involved in brassinosteroid signaling and controls bending of the lamina joint in rice

Brassinosteroids (BRs) are involved in many developmental processes and regulate many subsets of downstream genes throughout the plant kingdom. However, little is known about the BR signal transduction and response network in monocots. To identify novel BR-related genes in rice (Oryza sativa), we monitored the transcriptomic response of the brassinosteroid deficient1 (brd1) mutant, with a defective BR biosynthetic gene, to brassinolide treatment. Here, we describe a novel BR-induced rice gene BRASSINOSTEROID UPREGULATED1 (BU1), encoding a helix-loop-helix protein. Rice plants overexpressing BU1 (BU1:OX) showed enhanced bending of the lamina joint, increased grain size, and resistance to brassinazole, an inhibitor of BR biosynthesis. In contrast to BU1:OX, RNAi plants designed to repress both BU1 and its homologs displayed erect leaves. In addition, compared to the wild type, the induction of BU1 by exogenous brassinolide did not require de novo protein synthesis and it was weaker in a BR receptor mutant OsbriI (Oryza sativa brassinosteroid insensitive1, d61) and a rice G protein alpha subunit (RGA1) mutant d1. These results indicate that BU1 protein is a positive regulator of BR response: it controls bending of the lamina joint in rice and it is a novel primary response gene that participates in two BR signaling pathways through OsBRI1 and RGA1. Furthermore, expression analyses showed that BU1 is expressed in several organs including lamina joint, phloem, and epithelial cells in embryos. These results indicate that BU1 may participate in some other unknown processes modulated by BR in rice.

Investigation of heavy metal hyperaccumulation at the cellular level: development and characterization of Thlaspi caerulescens suspension cell lines

The ability of Thlaspi caerulescens, a zinc (Zn)/cadmium (Cd) hyperaccumulator, to accumulate extremely high foliar concentrations of toxic heavy metals requires coordination of uptake, transport, and sequestration to avoid damage to the photosynthetic machinery. The study of these metal hyperaccumulation processes at the cellular level in T. caerulescens has been hampered by the lack of a cellular system that mimics the whole plant, is easily transformable, and competent for longer term studies. Therefore, to better understand the contribution of the cellular physiology and molecular biology to Zn/Cd hyperaccumulation in the intact plant, T. caerulescens suspension cell lines were developed. Differences in cellular metal tolerance and accumulation between the cell lines of T. caerulescens and the related nonhyperaccumulator, Arabidopsis (Arabidopsis thaliana), were examined. A number of Zn/Cd transport-related differences between T. caerulescens and Arabidopsis cell lines were identified that also are seen in the whole plant. T. caerulescens suspension cell lines exhibited: (1) higher growth requirements for Zn; (2) much greater Zn and Cd tolerance; (3) enhanced expression of specific metal transport-related genes; and (4) significant differences in metal fluxes compared with Arabidopsis. One interesting feature exhibited by the T. caerulescens cell lines was that they accumulated less Zn and Cd than the Arabidopsis cell lines, most likely due to a greater metal efflux. This finding suggests that the T. caerulescens suspension cells represent cells of the Zn/Cd transport pathway between the root epidermis and leaf. We also show it is possible to stably transform T. caerulescens suspension cells, which will allow us to alter the expression of candidate hyperaccumulation genes and thus dissect the molecular and physiological processes underlying metal hyperaccumulation in T. caerulescens.

Strigolactones, host recognition signals for root parasitic plants and arbuscular mycorrhizal fungi, from Fabaceae plants

Both root parasitic plants and arbuscular mycorrhizal (AM) fungi take advantage of strigolactones, released from plant roots as signal molecules in the initial communication with host plants, in order to commence parasitism and mutualism, respectively. In this study, strigolactones in root exudates from 12 Fabaceae plants, including hydroponically grown white lupin (Lupinus albus), a nonhost of AM fungi, were characterized by comparing retention times of germination stimulants on reverse-phase high-performance liquid chromatography (HPLC) with those of standards and by using tandem mass spectrometry (LC/MS/MS). All the plant species examined were found to exude known strigolactones, such as orobanchol, orobanchyl acetate, and 5-deoxystrigol, suggesting that these strigolactones are widely distributed in the Fabaceae. It should be noted that even the nonmycotrophic L. albus exuded orobanchol, orobanchyl acetate, 5-deoxystrigol, and novel germination stimulants. By contrast to the mycotrophic Fabaceae plant Trifolium pratense, in which phosphorus deficiency promoted strigolactone exudation, neither phosphorus nor nitrogen deficiency increased exudation of these strigolactones in L. albus. Therefore, the regulation of strigolactone production and/or exudation seems to be closely related to the nutrient acquisition strategy of the plants.

Nitrogen deficiency as well as phosphorus deficiency in sorghum promotes the production and exudation of 5-deoxystrigol, the host recognition signal for arbuscular mycorrhizal fungi and root parasites

Strigolactones released from plant roots induce hyphal branching of symbiotic arbuscular mycorrhizal (AM) fungi and germination of root parasitic weeds, Striga and Orobanche spp. We already demonstrated that, in red clover plants (Trifolium pratense L.), a host for both AM fungi and the root holoparasitic plant Orobanche minor Sm., reduced supply of phosphorus (P) but not of other elements examined (N, K, Ca, Mg) in the culture medium significantly promoted the secretion of a strigolactone, orobanchol, by the roots of this plant. Here we show that in the case of sorghum [Sorghum bicolor (L.) Moench], a host of both the root hemiparasitic plant Striga hermonthica and AM fungi, N deficiency as well as P deficiency markedly enhanced the secretion of a strigolactone, 5-deoxystrigol. The 5-deoxystrigol content in sorghum root tissues also increased under both N deficiency and P deficiency, comparable to the increase in the root exudates. These results suggest that strigolactones may be rapidly released after their production in the roots. Unlike the situation in the roots, neither N nor P deficiency affected the low content of 5-deoxystrigol in sorghum shoot tissues.

Nitrogen deficiency as well as phosphorus deficiency in sorghum promotes the production and exudation of 5-deoxystrigol, the host recognition signal for arbuscular mycorrhizal fungi and root parasites

Strigolactones released from plant roots induce hyphal branching of symbiotic arbuscular mycorrhizal (AM) fungi and germination of root parasitic weeds, Striga and Orobanche spp. We already demonstrated that, in red clover plants (Trifolium pratense L.), a host for both AM fungi and the root holoparasitic plant Orobanche minor Sm., reduced supply of phosphorus (P) but not of other elements examined (N, K, Ca, Mg) in the culture medium significantly promoted the secretion of a strigolactone, orobanchol, by the roots of this plant. Here we show that in the case of sorghum [Sorghum bicolor (L.) Moench], a host of both the root hemiparasitic plant Striga hermonthica and AM fungi, N deficiency as well as P deficiency markedly enhanced the secretion of a strigolactone, 5-deoxystrigol. The 5-deoxystrigol content in sorghum root tissues also increased under both N deficiency and P deficiency, comparable to the increase in the root exudates. These results suggest that strigolactones may be rapidly released after their production in the roots. Unlike the situation in the roots, neither N nor P deficiency affected the low content of 5-deoxystrigol in sorghum shoot tissues.

Two-dimensional analysis of spurious modes in aluminum nitride film resonators

In this paper, a hybrid method, which combines the traditional concept of guided waves and the finite element method (FEM), is proposed to analyze the spurious modes of aluminum nitride (AIN) film with electrodes. First, the guided wave modes in the plated area are obtained by 1-D FEM. Second, a mode-match method is used to satisfy the boundary conditions. The vibration of the film resonator is a superposition of all of the guided modes. With respect to an A1N film resonator, which is a thickness-stretch mode resonator, we have identified three families of spurious modes: extension, thickness-stretch, and thickness-shear. The spectrum of spurious modes is calculated and the influence of the spurious modes is discussed.

Isolation and molecular characterization of a Spotted leaf 18 mutant by modified activation-tagging in rice

A lesion mimic mutant that we designated Spotted leaf 18 (Spl18) was isolated from 13,000 activation-tagging lines of rice produced by our modified activation-tagging vector and further characterized. Spl18 was dominant and its phenotype was linked to the T-DNA insertion. An ORF was located about 500 bp downstream of the inserted T-DNA, and the deduced protein, designated OsAT1, showed sequence similarity to an acyltransferase whose expression is induced by hypersensitive reaction in tobacco. The transcriptional level of OsAT1 was very low in the WT leaf blade but high in Spl18 leaf blade. In wild-type rice, OsAT1 was transcribed mainly in the young panicle, in the panicle just after heading, and in the leaf sheath. In addition, transcription of the genes for PR protein was upregulated in Spl18, accumulation of phytoalexins (both momilactone A and sakuranetin) was increased, and resistance to blast disease was improved. We then combined OsAT1 genomic DNA downstream of the modified 35S promoter and re-transformed it into rice. Lesion mimic and blast resistance phenotypes were detected in the transgenic lines produced, clearly indicating that overexpression of OsAT1 caused the Spl18 phenotypes. In addition, plants overexpressing OsAT1 showed resistance to bacterial blight.

Phosphorus deficiency in red clover promotes exudation of orobanchol, the signal for mycorrhizal symbionts and germination stimulant for root parasites

Plant derived sesquiterpene strigolactones, which have previously been characterized as germination stimulants for root parasitic plants, have recently been identified as the branching factors which induce hyphal branching morphogenesis, a critical step in host recognition by arbuscular mycorrhizal (AM) fungi. We show here that, in red clover plants (Trifolium pratense L.), which is known as a host for both AM fungi and the root holoparasitic plant Orobanche minor Sm., reduced supply of phosphorus (P) but not of other elements examined (N, K, Mg, Ca) in the culture medium significantly promotes the release of a strigolactone, orobanchol, by the roots of this plant. In red clover plants, the level of orobanchol exudation appeared to be regulated by P availability and was in good agreement with germination stimulation activity of the root exudates. This implies that under P deficiency, plant roots attract not only symbiotic fungi but also root parasitic plants through the release of strigolactones. This is the first report demonstrating that nutrient availability influences both symbiotic and parasitic interactions in the rhizosphere.

Phosphorus deficiency in red clover promotes exudation of orobanchol, the signal for mycorrhizal symbionts and germination stimulant for root parasites

Plant derived sesquiterpene strigolactones, which have previously been characterized as germination stimulants for root parasitic plants, have recently been identified as the branching factors which induce hyphal branching morphogenesis, a critical step in host recognition by arbuscular mycorrhizal (AM) fungi. We show here that, in red clover plants (Trifolium pratense L.), which is known as a host for both AM fungi and the root holoparasitic plant Orobanche minor Sm., reduced supply of phosphorus (P) but not of other elements examined (N, K, Mg, Ca) in the culture medium significantly promotes the release of a strigolactone, orobanchol, by the roots of this plant. In red clover plants, the level of orobanchol exudation appeared to be regulated by P availability and was in good agreement with germination stimulation activity of the root exudates. This implies that under P deficiency, plant roots attract not only symbiotic fungi but also root parasitic plants through the release of strigolactones. This is the first report demonstrating that nutrient availability influences both symbiotic and parasitic interactions in the rhizosphere.

Nonscanning measurements for determining in-plane mode shapes in piezoelectric devices with polished surfaces

A nonmechanical scanning method has been developed for the visualization of the in-plane mode shapes of piezoelectric devices with polished surfaces. By taking into account the reflection versus laser-wavelength characteristics of the material of the electrodes, the in-plane motion can be measured even if the surface of the measurement plane is polished like a mirror. This method is based on laser speckle interference and two-dimensional correlation filtering that effectively enhance the mode-shape visualization for bulk and surface acoustic wave devices. Although this method cannot directly measure absolute displacement, the simple measurement system and high speed measurement more than offset this disadvantage. The experimental results for fundamental thickness-shear and nearby inharmonic modes in a bimesa-shaped rectangular AT-cut quartz resonator have been presented. The results of the experiments and the analyses obtained by the three-dimensional finite element analyses correlate well and show the advantages and validity of the proposed technique.

[Difference between two wheat cultivars in Cd and mineral nutrient uptake under different Cd levels]

Cadmium pollution in soil not only affects growth and yield formation of crop plants, but also develops a potential risk to food health. The experiment was conducted to study growth of Cd and mineral nutrient uptake of two wheat cultivars differed in agronomic performance in seedling stage under 5 Cd levels ranged from 0 to 1.0 mg.kg-1 Cd. The results showed that the growth and dry matter accumulation were stimulated in low Cd concentration (0.03 mg.kg-1) for both cultivars, while inhibited significantly under high concentration (> 0.3 mg.kg-1). The inhibited extension was dependence on cultivars and Genguo 534 had higher tolerance to Cd toxicity in comparison with E18513. There was the significant interaction between Cd level and cultivar in the influence of Cd treatment on Cd content in both root and shoot in that Genguo 534 had higher Cd content in lower Cd levels and E81513 showed more rapid increase in higher Cd levels. Cd treatment had significant influence on mineral nutrient uptake and two cultivars showed different response. In the treatment of 0.1 mg.kg-1 Cd, the contents of five macro-nutrients were significant lower for E81513 in comparison with those in control, while Genguo remained little changed.

Effect of uncertainty in transfer rates for the ICPR publication 67 biokinetic model on dose estimation for 239Pu from results of individual monitoring. International Commission on Radiological Protection

The radiation dose due to internal exposures from 239Pu is mainly estimated by measuring actual urinary or faecal excretion of activity and comparing those values with the standard excretion rates calculated from the models of the International Commission on Radiological Protection (ICRP). Recently, on the other hand, uncertainties in the ICRP's models and parameters are under consideration because of the paucity of human data. In addition, there is a possibility of variation between individuals. A code has been developed to reproduce the ICRP's dose coefficients and excretion rates for 239Pu, which is one of the most important elements for occupational exposure. By using this code, the respective transfer rates for the ICRP Publication 67 biokinetic model were modified, and the effect owing to these changes on present hazard assessment was investigated. As a result, it was shown that dose estimates for workers exposed to 239Pu were not very sensitive to changes in these transfer rates.

Analysis of 3-D vibrations of rectangular AT-cut quartz plates with a bi-mesa structure

A method to analyze 3-D vibrations of rectangular AT-cut quartz bi-mesa-shaped plates is developed. The method is based on a classical approach. As in 2-D analysis, the half structure of a plate is separated into a thick bi-mesa and a thin-side portion, and the displacement field of each region is represented by a linear combination of guided waves. In the 3-D analysis, we apply the 2-D finite element method (FEM) to obtain the waves guided by two pairs of parallel surfaces. The orthogonal property of guided modes is incorporated to approximately fulfill the continuity conditions at the interface between the thick and thin portions. The stress-free conditions on the plate edges are satisfied by employing the method of weighted residuals (MWR). The computational advantage of this method is that it can greatly reduce the matrix size compared with the 3-D FEM. As a numerical example, the frequency spectra are calculated for X-elongated plates of bi-mesa shape, and the strong energy-trapping effect on the fundamental thickness-shear (TS) resonance is verified.

Effect of membrane surface charge on nickel uptake by purified mung bean root protoplasts

The influence of membrane surface charge on cation uptake was investigated in protoplasts prepared from roots of mung bean (Vigna radiata L.). Confocal laser scanning microscopy showed that a fluorescent trivalent cation accumulated to very high concentrations at the surface of the protoplasts when they were incubated in medium containing low concentrations of Ca or other cations, but that this accumulation could be completely reversed by suppression of membrane surface negativity by high cation concentrations. Influx of 63Ni was strongly reduced by a range of divalent cations. Increasing the Ca concentration in the medium from 25 microM to 10 mM inhibited 63Ni influx by more than 85%. 63Ni influx was also inhibited by 85% by reducing the pH from 7 to 4. Computation of the activity of Ni at the membrane surface under the various treatment conditions showed that Ni uptake was closely correlated with its activity at the membrane surface but not with its concentration in the bulk medium. It was concluded that the effects on Ni uptake of addition of monovalent, divalent and trivalent cations, and of variations in pH are all consistent with the proposition that the activity of Ni at the membrane surface is the major determinant of the rate of Ni influx into mung bean protoplasts. It is proposed that the surface charge on the plasma membrane will influence the membrane transport of most charged molecules into cells.

Src family tyrosine kinases participate in insulin-like growth factor I mitogenic signaling in 3T3-L1 cells

Insulin-like growth factor-I (IGF-I) stimulates proliferation and differentiation of many cell types, including preadipocytes. We have previously shown that IGF-I stimulates proliferation of 3T3-L1 preadipocytes through activation of the extracellular regulated kinase (ERK)-1 and -2 mitogen-activated protein kinase (MAPK) pathway, and that IGF-I-stimulated MAPK is predominantly downstream of Shc, not IRS-1 phosphorylation. The Src family of nonreceptor tyrosine kinases has been shown to mediate the mitogenic effects of other growth factors that also activate Shc and the ERK-1 and -2 MAPKs. Although Src family kinases (SFK) have been implicated in IGF-I action, no specific role for SFKs in IGF-I regulation of mitogenesis has been previously demonstrated. We studied the role of SFKs in IGF-I mitogenic signaling in 3T3-L1 preadipocytes. The SFK-selective inhibitor PP1 completely inhibited both IGF-I-stimulated DNA synthesis and MAPK activation in proliferating 3T3-L1 cells. PP1 inhibited IGF-I phosphorylation of Shc but not of IRS-1. In addition, IGF-I activation of MAPK was inhibited in proliferating cells transiently transfected with a dominant-negative c-Src. Finally, the kinetics of SFK and MAPK activation by IGF-I suggest that SFKs may act upstream of MAPK. IGF-I activation of SFK members c-Src and Fyn occurred within 1 min of treatment, and activity was back to baseline by 10 min. Our previous studies found that IGF-I activation of MAPK peaked at 5 min and was also back to baseline by 10 min. Our results are the first to demonstrate that SFKs mediate IGF-I mitogenic signaling in 3T3-L1 cells and add to the growing body of evidence that SFKs play a crucial role in IGF-I action.

Dependence of dose coefficients for inhaled 239Pu on absorption parameters

With regard to dissolution of particles in the respiratory tract after inhalation, the International Commission on Radiological Protection (ICRP) has classified all radionuclides into only three types according to the chemical form of compounds, and default values of absorption parameters are proposed for each type. However, it is just a simplification to estimate doses for practical use, and there is a possibility of unfitness in such an assortment. A code has been developed to reproduce the ICRP's dose coefficients for 239Pu, which is one of the most important elements for occupational exposure. By using this code, the respective absorption parameters were modified, and the effect owing to these changes evaluated. It was shown consequently that changes of absorption parameters do not greatly influence the effective doses of 239Pu for workers.

Prenatal findings in Brachmann-de Lange syndrome

We present a case of Brachmann-de Lange syndrome, in which prenatal ultrasonographic evaluation demonstrated increased nuchal translucency, early onset of intrauterine growth retardation, and limb abnormalities in the first, second, and third trimester, respectively.