Effects of root exudates of Rj2Rj3- and Rj4-genotype soybeans on growth and chemotaxis of Bradyrhizobium japonicum

Almost all of the soybean cultivars (Glycine max L. Merr.) form nodules on their roots by infection with Bradyrhizobium japonicum. However, it has been observed that the soybean cultivars harboring nodulation conditioning genes, for instance Rj ₂, Rj ₃, and Rj ₄, do not form effective nodules with some strains of B. japonicum. Ishizuka et al. (1991b) classified the rhizobia isolated from field-grown soybeans into nodulation-types A, B, and C based on the compatibility with these Rj-soybean cultivars. Nodulation-type B is incompatible with Rj ₂ Rj ₃-cultivars and type C is incompatible with Rj ₄-cultivars. Nodulation-type A rhizobia are compatible with both Rj ₂ Rj ₃ - and Rj ₄-cultivars. Furthermore, the Rj-cultivars were found to prefer appropriate nodulation-type rhizobia for nodulation, that is, non-Rj-, Rj ₂ Rj ₃ -, and Rj ₄-cultivars prefer nodulation-types A, C, and B rhizobia, respectively (Ishizuka et al. 1991a). In the present study, in order to examine the mechanisms of preference of Rj-cultivars for rhizobial strains for nodulation, root exudates from Rj-cultivars were examined for their effects on the growth rate and chemotaxis of various types of B. japonicum strains.     

Feasibility study on water solubilization of spawned out salmon meat by conjugation with alginate oligosaccharide

A feasibility study was carried out to determine whether water-soluble salmon meat could be manufactured by conjugating a glycosyl unit using the Maillard reaction. Spawned out salmon meat was washed, mixed with alginate oligosaccharide (AO) and sorbitol, lyophilized, and then heated at 60°C and 5–95% relative humidity (RH) to introduce AO (the mean degree of polymerization was six) into the myofibrillar proteins through the Maillard reaction. The reaction progressed with an increase in the reaction humidity and the amount of AO bound to the protein reached >150 μg/mg at RH 65 and 90%. However, the protein glycosylation under high humidity impaired protein solubility and the meat protein became effectively water-soluble with the conjugation with AO at reaction conditions of 60°C and RH 35%. The improved characteristics of the meat protein were highly stable at room temperature. Further, the water-soluble protein can be prepared from the frozen salmon meat stored at −25°C for 60–90 days. These results indicate that protein glycosylation has strong potential for use with spawned out chum salmon. The suppression of protein denaturation during processing is important to obtain the high water-soluble meat protein.     

Pond area and distance from continuous forests affect amphibian egg distributions in urban green spaces: A case study in Sapporo,Japan

We examined factors that affect egg distributions of amphibians, which are currently declining globally, in urban areas. We counted the number of egg masses of two amphibian species (Hynobius retardatus and Rana pirica) in ponds in urban green spaces during two years (2011 and 2012) and investigated the effects of local and landscape factors on them. Forest area in green spaces and pond area had positive effects, and distance from continuous forests in the suburbs and the rate of pond shore protection had negative effects on the number of eggs. Among these factors, distance from continuous forests and pond area had strong effects on egg distributions. These results suggest the importance of water habitat size and the need for colonization by amphibians from surrounding continuous forests. To conserve urban amphibian assemblages, the preservation of ponds with sufficient area and continuous forests close to urban habitats would be important.     

Seasonal changes and controlling factors of gross N transformation in an evergreen plantation forest in central Japan

We conducted a year-round measurement of gross N transformation rates using the ¹⁵N dilution method, and analyzed seasonal changes and the mechanisms regulating gross N transformation in the Kiryu Experimental Forest in central Japan. While soil microbial biomass C (SMB-C) decreased from the dormant to growing seasons at the organic (O) horizon, no significant trend was observed in SMB-N. This resulted in SMB-C/N being high in the dormant season and low in the growing season, and suggests that the microbial composition changed seasonally. No clear seasonal trend was found in gross NH₄ ⁺ production rates at either the O or surface mineral soil horizons. In contrast, the NH₄ ⁺ consumption rate varied seasonally, with high values in January and April during the dormant season and low values in July and October during the growing season. There was no clear trend in seasonal fluctuation of net NH₄ ⁺ production rates. Gross NH₄ ⁺ production and gross NH₄ ⁺ consumption rates were 10 times greater than the gross nitrification rate. Almost all of the produced NH₄ ⁺ was immobilized, indicating that N tightly cycles at this study site. Considered together with results of the gross N transformation rates, the dominance of high SMB-C/N microbes might stimulate immobilization in the dormant season. At this study site, the change in microbial composition likely influences gross N transformation through immobilization efficiency.     

Detection of telomere length and oxidative stress in Chondrichthyes

Telomeres, repeating TTAGGG sequences at the ends of eukaryotic chromosomes, increase genomic stability. Telomere shortening occurs not only during DNA replication associated with cell division but also under oxidative stress, where reactive oxygen species damage DNA. Therefore, changes in telomere length can be used to evaluate chronic cost or stress responses incurred by individuals. The phylogenetically unique Chondrichthyes are among the least-studied groups of marine vertebrates. Telomere data are limited and have only been reported in a few Chondrichthyes species. In this study, we measured telomere length and quantified oxidative stress and antioxidant power in 17 Chondrichthyes species whose telomere length has not been measured before. The presence of telomere sequences?>?30 bp and lower values of oxidative stress were confirmed in most species. Average telomere length was not correlated with oxidative stress and antioxidant power in 15 species for which both measurements were available. It would be desirable in the future to elucidate the nature of telomeres in Chondrichthyes, and their direct relationship with reactive oxygen species.

     

Pathogenic diversity of soybean rust in Argentina, Brazil, and Paraguay

Phakopsora pachyrhizi, the cause of soybean rust, is an economically important pathogen of soybean in South America. Understanding the pathogenicity of indigenous fungal populations is useful for identifying resistant plant genotypes and targeting effective cultivars against certain populations. Fifty-nine rust populations from Argentina, Brazil, and Paraguay were evaluated for pathogenicity in three cropping seasons, 2007/2008–2009/2010, using 16 soybean differentials. Only two pairs of P. pachyrhizi populations displayed identical pathogenicity profiles, indicating substantial pathogenic variation in the rust populations. Comparative analysis of 59 South American and five Japanese samples revealed that pathogenic differences were not only detected within South America but also distinct between the P. pachyrhizi populations from South America and Japan. In addition, seasonal changes in rust pathogenicity were detected during the sampling period. The differentials containing resistance genes (Rpp: resistance to P. p achyrhizi) Rpp1, Rpp2, Rpp3, and Rpp4, except for Plant Introduction (PI) 587880A, displayed a resistant reaction to only 1.8–14, 24–28, 22, and 36 % of South American P. pachyrhizi populations, respectively. In contrast, PI 587880A (Rpp1), Shiranui (Rpp5), and 3 Rpp-unknown differentials (PI 587855, PI 587905, and PI 594767A) showed a resistant reaction to 78–96 % of all populations. This study demonstrated that P. pachyrhizi populations from South America vary geographically and temporally in pathogenicity and that the known Rpp genes other than Rpp1 in PI 587880A and Rpp5 have been less effective against recent pathogen populations in the countries studied.