Rj (rj) genes involved in nitrogen-fixing root nodule formation in soybean

It has long been known that formation of symbiotic root nodules in soybean (Glycine max (L.) Merr.) is controlled by several host genes referred to as Rj (rj) genes, but molecular cloning of these genes has been hampered by soybean’s complicated genome structure and large genome size. Progress in molecular identification of legume genes involved in root nodule symbiosis have been mostly achieved by using two model legumes, Lotus japonicus and Medicago truncatula, that have relatively simple and small genomes and are capable of molecular transfection. However, recent development of resources for soybean molecular genetic research, such as genome sequencing, large EST databases, and high-density linkage maps, have enabled us to isolate several Rj genes. This progress has been achieved in connection with systematic utilization of the information obtained from molecular genetics of the model legumes. In this review, we summarize the current status of knowledge of host-controlled nodulation in soybean based on information from recent studies on Rj genes, and discuss the future research prospects.     

Mapping the relative risk of surface water acidification based on cumulative acid deposition over the past 25 years in Japan

Sensitivity maps of atmospheric acid deposition in Japan have not been updated in 20 years. Here, we propose new relative risk maps of surface water acidification in forests based on a weighted overlay of cumulative potential acid deposition (CPAD) simulated for a 25-year period (1981–2005), including the sensitivities of soil and bedrock to acidification. We assumed that relative acidification risk is high in areas that exhibit high sensitivities of soil and bedrock to acid and have received a large amount of cumulative acid deposition over the past several decades. We aggregated fine soil and bedrock maps into a 20-km mesh for overlay onto an 80-km mesh map of CPAD by considering their spatial structures in Japan. Allocation of the weights among CPAD and soil and bedrock sensitivities was performed based on observational trends in river pH over the past 30 years. The resulting risk map for surface water acidification showed that large areas of western Japan, as well as smaller areas of Hokkaido, Tohoku, Kanto, and Kyushu, are at high risk of surface water acidification. Seventy-seven percent of all rivers for which a declining trend in pH was observed from 2001 to 2009 were also high-risk areas. Acid deposition might be one factor controlling surface water acidification in areas with high bedrock sensitivity, in addition to high CPAD and soil sensitivity, although the risk of soil acidification remains unclear.     

Overexpression of xyloglucanase (AaXEG2) accelerates heteroblastic development in mangium leaves

Transgenic mangium trees (Acacia mangium) overexpressing xyloglucanase (AaXEG2) were generated by spraying flower buds with Agrobacterium solution and allowing seeds to develop. The overexpression of xyloglucanase decreased xyloglucan content in the cell walls and increased stem length and diameter. The leaves of the transgenic seedlings exhibited accelerated heteroblastic development, proceeding from the stage of three bipinnate leaves to that of enlarging petiole 2 weeks earlier than wild type seedlings did.     

Effects of Additional Layer(s) on the Mobility of Arsenic from Hydrothermally Altered Rock in Laboratory Column Experiments

Hydrothermally altered rocks are frequently encountered when tunnels are constructed in Hokkaido, Japan. High concentraions of hazardous elements, such as arsenic (As), are often released from these rocks into the surrounding environments. Therefore, the rocks are considered potentially hazardous waste. This article describes the effects of water content and oxygen (O₂) concentration in relation to additional layer(s), i.e., surface covering and bottom adsorption layers, on As leaching by using laboratory columns with water content and O₂ concentration sensors. The results show that the use of additional layer(s) has a significant effect on lowering As migration. This was due not only to the adsorption capacity of As by the adsorption layer but also to the water content and O₂ concentration inside the rock layer. The accumulation of pore water was increased in the rock layer in cases with additional layer(s), which resulted in lower O₂ concentration in the rock layer. Consequently, the leaching of As by the oxidation of As-bearing minerals in the rock layer was reduced. Moreover, a longer water-resident time in the rock layer may induce precipitation of Fe oxy-hydroxide/oxide. These results suggest that the geochemical conditions of the rock layer affect As leaching and migration.     

Evaluation of the umami taste intensity of green tea by a taste sensor

A method for evaluating the umami taste intensity of green tea by a taste sensor system was established. Interference in the measurement from catechins was solved by removing the catechins from sample solutions with poly(vinylpolypyrrolidone). A 5.00 mM aqueous solution of glutamic acid monosodium salt was used as the standard solution. Sensor outputs were converted into EIT uma (estimated intensity of taste concerning umami) values. One unit on the EIT uma scale was defined as the amount of the sensor output corresponding to a difference in 1.2 times the concentration of the standard substance (glutamic acid monosodium salt). The umami taste intensity of green tea was classified into six grades on the EIT uma scale. Sensory tests proved that the EIT uma value had a high correlation to the human gustatory sense.     

Distribution and characterization of enzymes causing starch degradation in rice (Oryza sativa cv. koshihikari)

The thermal dependency and stability of enzymes producing reducing sugar (RS) were examined in bran, the exterior 13% part (outer endosperm), and the remaining inner endosperm of rice grains. RS-producing enzymes in the inner endosperm showed a higher optimum temperature than those in other parts of the rice grain. Diethylaminoethyl-Sephacel chromatography of crude extracts revealed two peaks of RS-producing activity with different optimum temperatures (60 and 37 degrees C) in all three parts. alpha-Glucosidase (EC 3.2.1.20) and alpha-amylase (EC 3.2.1.1) isoform G were thought to be major components of the RS-producing activities with high and low optimum temperatures, respectively. The peak with a high optimum temperature was a more abundant component in the inner endosperm, compared with other parts of the rice grain. Thus, different parts of rice were found to have distinct enzyme sets having different thermal dependency and to be involved in starch degradation to various sugars.     

Genetic Variation of Blast Resistance in Foxtail Millet (<Emphasis Type="Italic">Setaria italica</Emphasis> (L.) P. Beauv.) and its Geographic Distribution

To clarify the geographic variation and isolate specificity in blast resistance, 20 cultivars of foxtail millet (Setaria italica (L.) P. Beauv.) originating from Eurasia were examined for their resistance using 11 Japanese Setaria isolates of blast fungus. Cultivars from the countries east of Pakistan generally showed resistance to most of the 11 fungus isolates, whereas those from the countries west of Afghanistan indicated higher susceptibility. The origin of this geographical regularity was discussed in relation to the deficiency or specificity of relevant resistance gene(s). No identical reaction pattern was observed among cultivars, indicating their highly distinctive isolate specificity. The virulence of isolates was also diverse, since only 2 out of 10 virulent isolates were identical for their reaction patterns. Preliminary genetic analysis of blast resistance to four fungus isolates suggests that they are governed by more than two dominant genes.     

Evaluation of the utilization of heated sewage sludge for peri-urban horticulture production in the Sahel of West Africa

Shortage of organic matter hinders agricultural production in the Sahel, and this lack of enough organic matter is more severe for peri-urban horticulture, which depends heavily on it. Alternative sources of organic matter that offer new options for peri-urban horticulture can help reduce the potential for conflict over finite resources between traditional crop production and peri-urban horticulture. Both agronomic and economic evaluations of an organic amendment called heated sewage sludge (HSS) were conducted in the research station of International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)-Niamey, Niger, West Africa. For this study, HSS, a material imported from Japan, applied at a dosage application equivalent to 20.0 kg 100 m⁻² on lettuce fields led to production levels as high as those of conventional methods, and the yield became even higher than those of conventional methods when the dosage was increased to 50.0 kg 100 m⁻² and 100.0 kg 100 m⁻². Even though HSS was imported, its benefits outweighed its cost, as evidenced by the positive net returns. Since profitability in peri-urban horticulture is much higher than that of traditional crop production, the results of this study imply that if adopted, the use of HSS can lead to increased availability of organic matter for traditional cropping systems.     

Nonsense mutation of feline beta-hexosaminidase beta-subunit (HEXB) gene causing Sandhoff disease in a family of Japanese domestic cats

G(M2) gangliosidoses are inherited metabolic disorders and are caused by severely reduced enzymatic activity of lysosomal beta-hexosaminidase. In the present study, the open reading frame (ORF) of the HEXB gene in a family of Japanese domestic cats with G(M2) gangliosidosis variant 0 (Sandhoff disease) was determined. Two types of abnormal cDNA clones were obtained from the liver of an affected cat tissue. One showed a single nucleotide substitution from C to T at nucleotide position 667 of the HEXB ORF. In the deduced amino acid sequence, the codon of arginine was altered to a stop codon. The genotyping, using PCR-primer introduced restriction analysis confirmed that Sandhoff disease in this family is associated with this nonsense mutation. Discovery of the nonsense mutation will permit the confirmation of the clinical diagnosis of Sandhoff disease in conjugation with the already established enzyme-based test.