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Mizobuchi R.,Japan National Institute of Agrobiological Science | Sato H.,Japan National Agriculture and Food Research Organization | Fukuoka S.,Japan National Institute of Agrobiological Science | Tanabata T.,Japan National Institute of Agrobiological Science | And 4 more authors.
Rice | Year: 2013

Background: Bacterial grain rot (BGR), caused by the bacterial pathogen Burkholderia glumae, is a destructive disease of rice. Because BGR tends to be highly affected by environmental conditions such as temperature and humidity, it is difficult to evaluate BGR resistance of diverse cultivars with different heading dates by using field inoculation. Molecular tagging of genes involved in BGR is an important objective for rice breeding. Results: In this study, we mapped a quantitative trait locus (QTL) for BGR resistance by a modified cut-panicle inoculation method. First, we assessed the levels of BGR resistance in 84 cultivars by a standard cut-panicle inoculation technique, in which panicles are harvested and inoculated in the laboratory under controlled conditions. For the genetic analysis, we selected two cultivars: Kele, a resistant traditional lowland cultivar (indica) that originated in India, and Hitomebore, a susceptible modern lowland cultivar (temperate japonica) from Japan. Second, by comparing the susceptibility of Kele and Hitomebore spikelets before and up to 3 days after anthesis, we found a dramatic decline in susceptibility at 1 day after anthesis in Kele but not in Hitomebore. Thus, we applied a modified method by inoculating spikelets at 1 day after anthesis for further analysis. To search for QTLs associated with BGR resistance, we measured the ratio of diseased spikelets (RDS, an index reflecting both quantity and severity of infection) and the ratio of diseased spikelet area (RDSA) in 110 backcrossed inbred lines (BILs) derived from a cross between Kele and Hitomebore. One major QTL associated with both RDS and RDSA was detected on the long arm of chromosome 1. This QTL explained 25.7% and 12.1% of the total phenotypic variance in RDS and RDSA in the BILs, respectively, and the Kele allele increased BGR resistance. Conclusions: We mapped a major QTL for BGR resistance on the long arm of chromosome 1. These results clearly demonstrated that genetic analysis of BGR resistance in rice can be effectively performed and that this trait could be a target of marker-assisted selection in rice breeding programs. © 2013 Mizobuchi et al.; licensee Springer.


Mizobuchi R.,Japan National Institute of Agrobiological Science | Sato H.,Japan National Agriculture and Food Research Organization | Fukuoka S.,Japan National Institute of Agrobiological Science | Tsushima S.,Japan National Institute for Agro - Environmental Sciences | And 2 more authors.
Theoretical and Applied Genetics | Year: 2013

Bacterial seedling rot (BSR), a destructive disease of rice (Oryza sativa L.), is caused by the bacterial pathogen Burkholderia glumae. To identify QTLs for resistance to BSR, we conducted a QTL analysis using chromosome segment substitution lines (CSSLs) derived from a cross between Nona Bokra (resistant) and Koshihikari (susceptible). Comparison of the levels of BSR in the CSSLs and their recurrent parent, Koshihikari, revealed that a region on chromosome 10 was associated with resistance. Further genetic analyses using an F5 population derived from a cross between a resistant CSSL and Koshihikari confirmed that a QTL for BSR resistance was located on the short arm of chromosome 10. The Nona Bokra allele was associated with resistance to BSR. Substitution mapping in the Koshihikari genetic background demonstrated that the QTL, here designated as qRBS1 (quantitative trait locus for RESISTANCE TO BACTERIAL SEEDLING ROT 1), was located in a 393-kb interval (based on the Nipponbare reference genome sequence) defined by simple sequence repeat markers RM24930 and RM24944. © 2013 The Author(s).


PubMed | National Agricultural and Food Research Organization, University of the Philippines at Los Baños, Hokkaido University, Cavite State University and 2 more.
Type: | Journal: Developmental and comparative immunology | Year: 2016

Tick defensins are antimicrobial peptides that play a major role in the innate immunity of ticks by providing a direct antimicrobial defense. In this study, we identified and characterized a defensin-like encoding gene, HEdefensin, from the expressed sequence tags (EST) database of hemolymph from the hard tick Haemaphysalis longicornis. Expression of the gene in whole adult ticks and in different organs was upregulated during blood feeding, though not after Langat virus (LGTV) challenge. A synthetic HEdefensin peptide demonstrated significant virucidal activity against LGTV but not against an adenovirus in co-incubation virucidal assays. Moreover, the RNAi-mediated gene silencing of HEdefensin did not significantly affect the virus titer as compared to the control group. The data reported here have established the invitro virucidal activity of the peptide against LGTV. However, its role in the innate antiviral immunity of H. longicornis remains to be explored, and further studies are needed to fully evaluate the potential biological activities of the peptide against bacteria, fungi or parasites.


Maeda H.,Kagoshima University | Boldbaatar D.,Kagoshima University | Kusakisako K.,Kagoshima University | Galay R.L.,Kagoshima University | And 8 more authors.
Parasitology Research | Year: 2013

Haemaphysalis longicornis is known as one of the most important ticks transmitting Babesia parasites in East Asian countries, including Babesia ovata and Babesia gibsoni, as well as Theileria parasites. H. longicornis is not the natural vector of Babesia bovis and Babesia bigemina. Vector ticks and transmitted parasites are thought to have established unique host-parasite interaction for their survival, meaning that vector ticks may have defensive molecules for the growth control of parasites in their bodies. However, the precise adaptation mechanism of tick-Babesia parasites is still unknown. Recently, cyclophilin A (CyPA) was reported to be important for the development of Babesia parasites in ticks. To reveal a part of their adaptation mechanism, the current study was conducted. An injection of B. bovis-infected RBCs into adult female H. longicornis ticks was found to upregulate the expression profiles of the gene and protein of CyPA in H. longicornis (HlCyPA). In addition, recombinant HlCyPA (rHlCyPA) purified from Escherichia coli exhibited significant inhibitory growth effects on B. bovis and B. bigemina cultivated in vitro, without any hemolytic effect on bovine RBCs at all concentrations used. In conclusion, our results suggest that HlCyPA might play an important role in the growth regulation of Babesia parasites in H. longicornis ticks, during natural acquisition from an infected host. Furthermore, rHlCyPA may be a potential alternative chemotherapeutic agent against babesiosis. © 2013 Springer-Verlag Berlin Heidelberg.


Galay R.L.,Yamaguchi University | Galay R.L.,Kagoshima University | Umemiya-Shirafuji R.,Obihiro University of Agriculture and Veterinary Medicine | Mochizuki M.,Yamaguchi University | And 4 more authors.
Parasitology International | Year: 2015

Ticks are notorious parasitic arthropods, known for their completely host-blood-dependent lifestyle. Hard ticks (Acari: Ixodidae) feed on their hosts for several days and can ingest blood more than a hundred times their unfed weight. Their blood-feeding habit facilitates the transmission of various pathogens. It is remarkable how hard ticks cope with the toxic nature of their blood meal, which contains several molecules that can promote oxidative stress including iron. While it is required in several physiological processes, high amounts of iron can be dangerous because iron can also participate in the formation of free radicals that may cause cellular damage and death. Here we review the current knowledge on heme and inorganic iron metabolism in hard ticks and compare it with that in vertebrates and other arthropods. We briefly discuss the studies on heme transport, storage and detoxification, and the transport and storage of inorganic iron, with emphasis on the functions of tick ferritins. This review points out other aspects of tick iron metabolism that warrant further investigation, as compared to mammals and other arthropods. Further understanding of this physiological process may help in formulating new control strategies for tick infestation and the spread of tick-borne diseases. © 2014 Elsevier Ireland Ltd.


PubMed | Kitasato University, Yamaguchi University, National Agricultural and Food Research Organization, Kagoshima University and Obihiro University of Agriculture and Veterinary Medicine
Type: | Journal: Parasites & vectors | Year: 2015

Tick control is an essential aspect of controlling the spread of tick-borne diseases affecting humans and animals, but it presently faces several challenges. Development of an anti-tick vaccine is aimed at designing cost-effective and environmentally friendly protection against ticks and tick-borne diseases as an alternative to the use of chemical acaricides. A single vaccine from the tick midgut protein Bm86 is currently available for field applications, but its efficacy is limited to only some tick species. Identification of candidate vaccine antigens that can affect multiple tick species is highly desirable. The hard tick Haemaphysalis longicornis has two kinds of the iron-binding protein ferritin (HlFER), an intracellular HlFER1 and a secretory HlFER2, and RNA interference experiments showed that these are physiologically important in blood feeding and reproduction and in protection against oxidative stress. Here we investigated the potential of targeting HlFERs for tick control by immunizing the host with recombinant HlFERs (rHlFER1 and rHlFER2).Rabbits were immunized with rHlFERs three times subcutaneously at two-week intervals. Antisera were collected before the first immunization and a week after each immunization to confirm the antigen-specific serum antibody titer by serum ELISA. Two weeks after the final immunization, the rabbits were challenged with tick infestation. After dropping, tick feeding and reproduction parameters were evaluated to determine vaccine efficacy. To demonstrate the effects of antibodies, oxidative stress was detected in the eggs and larvae.The antibody titer of rHlFER-immunized rabbits greatly increased after the second immunization. Antibodies exhibited cross-reactivity with rHlFERs and reacted with tick native HlFERs in Western blot analysis. Significantly lower bodyweight was observed in the ticks infested from the rHlFER2-immunized rabbit compared to those from the control rabbit. Reduced oviposition and hatching rate were observed in both rHlFER-immunized groups. rHlFER2 showed a higher vaccine efficacy. The antibodies against rHlFERs were detected in the eggs, and higher levels of oxidative stress biomarkers in the eggs and larvae, of ticks from rHlFER vaccinated rabbits.Collectively, these results showed that HlFER2 has a good potential as an anti-tick vaccine antigen that may affect multiple tick species.


PubMed | Kagoshima University, National Agricultural and Food Research Organization, Yamaguchi University and Obihiro University of Agriculture and Veterinary Medicine
Type: Journal Article | Journal: Ticks and tick-borne diseases | Year: 2014

Transferrin is known to be an iron transporter in vertebrates and several arthropods. Iron from host blood is essential for ovarian development in blood-sucking arthropods. However, tick transferrin has been identified in only a few species, and its function has yet to be elucidated, resulting in incomplete understanding of iron metabolism in ticks. Here, we investigated the transfer of host-derived transferrin in the hard tick Haemaphysalis longicornis using immunological methods. Western blot showed that host-derived transferrin was maintained in all developmental stages of ticks up to 28 days after engorgement and was detected in the midgut and the ovary of adult females following blood feeding. However, no host-derived transferrin was detected in eggs after laying or in larvae after hatching, indicating that host-derived transferrin is not transferred to offspring transovarially. Indirect immunofluorescent antibody testing showed the localization of host-derived transferrin in digestive cells of the midgut and oocytes of the ovary from engorged adult females. These results suggest that host-derived transferrin is transferred to the ovary through the midgut and the hemolymph, and raise the possibility of the function of host-derived transferrin as an iron source in the ovary, providing additional insight on iron metabolism in ticks.


PubMed | Kagoshima University, National Agricultural and Food Research Organization and Obihiro University of Agriculture and Veterinary Medicine
Type: | Journal: Methods in molecular biology (Clifton, N.J.) | Year: 2016

Ticks (Parasitiformes: Ixodida) are known for their obligate blood feeding habit and their role in transmitting pathogens to various vertebrate hosts. Tick control using chemical acaricides is extensively used particularly in livestock management, but several disadvantages arise from resistance development of many tick species, and concerns on animal product and environmental contamination. Vaccination offers better protection and more cost-effective alternative to application of chemical acaricides, addressing their disadvantages. However, an ideal anti-tick vaccine targeting multiple tick species and all the tick stages is still wanting. Here, we describe the procedures involved in the evaluation of a vaccine candidate antigen against ticks at the laboratory level, from the preparation of recombinant proteins, administration to the rabbit host and monitoring of antibody titer, to tick infestation challenge and determination of the effects of immunization to ticks.


Kamiji Y.,Tokyo University of Agriculture | Yoshida H.,National Agricultural and Food Research Organization | Palta J.A.,CSIRO | Sakuratani T.,Tokyo University of Agriculture | Shiraiwa T.,Kyoto University
Field Crops Research | Year: 2011

Efficient use of nitrogen fertilizer is critical in improving yield stability in rice. The objective of this study was to determine the effect of nitrogen (N) top-dressing on the number of total spikelet (fertile plus sterile) production and evaluate the effect among rice cultivars. We analyzed 136 sets of experimental data on growth and spikelet production for three lowland cultivars, grown under various regimes of N over 10 seasons at Kyoto, Ibaraki and Kanagawa, Japan. In each season, one to three of the lowland cultivars, Nipponbare (japonica), Koshihikari (japonica) and Takanari (indica), were studied. In 1986, 1995 and 1999-2001, the N regimes included basal application only, light basal and heavy top-dressing from the panicle initiation stage onward, heavy basal and heavy top-dressing from the spikelet formation stage onward, and no applications. In 2002 and 2005-2008, we set up experimental plots with varied time of N top-dressing, with or without N basal application. Takanari had the largest spikelet number averaged over all plots and was considered better efficient in spikelet production per applied N than the other cultivars. Although the trend is not clear, the effect of time of top-dressing on spikelet number was generally the greatest when N was top-dressed from 35 to 30 days before heading. The variation of observed spikelet number was analyzed with a linear regression of plant N 14 days before heading and by a model that estimates spikelet production accounting for plant N 14 days before heading and crop growth rate (CGR) during the 14-day period preceding heading. For the variation of spikelet number within each cultivar, the linear function model expressed the observed spikelet number than the two function model with R2 0.43$$ versus 0.13$-0.28$$ for the former and later models, respectively. When the results of all cultivars were combined, the two function model was much better for estimation of spikelet number than the linear function model (R2=0.36$$ vs. 0.20$). This indicates that yearly and varietal variation of spikelet number was caused mainly by plant N status at the late spikelet differentiation stage. The varietal variation in spikelet production efficiency is explained by CGR during this 14-day period. We concluded that N applications that increase plant N 14 days before heading is highly effective in maximizing spikelet production among cultivars. © 2011 Elsevier B.V.


Yoshida T.,University of Arizona | Yoshida T.,National Agricultural and Food Research Organization | Troch P.A.,University of Arizona
Hydrology and Earth System Sciences | Year: 2016

Present-day landscapes have evolved over time through interactions between the prevailing climates and geological settings. Understanding the linkage between spatial patterns of landforms, soils, and vegetation in landscapes and their hydrological response is critical to make quantitative predictions in ungaged basins. Catchment coevolution is a theoretical framework that seeks to formulate hypotheses about the mechanisms and conditions that determine the historical development of catchments and how such evolution affects their hydrological response. In this study, we selected 14 volcanic catchments of different ages (from 0.225 to 82.2 Ma) in Japan. We derived indices of landscape properties (drainage density and slope-area relationship) as well as hydrological response (annual water balance, baseflow index, and flow-duration curves) and examined their relation with catchment age and climate (through the aridity index). We found a significant correlation between drainage density and baseflow index with age, but not with climate. The intra-annual flow variability was also significantly related to catchments age. Younger catchments tended to have lower peak flows and higher low flows, while older catchments exhibited more flashy runoff. The decrease in baseflow with catchment age is consistent with the existing hypothesis that in volcanic landscapes the major flow pathways change over time from deep groundwater flow to shallow subsurface flow. The drainage density of our catchments decreased with age, contrary to previous findings in a set of similar, but younger volcanic catchments in the Oregon Cascades, in which drainage density increased with age. In that case, older catchments were thought to show more landscape incision due to increasing near-surface lateral flow paths. Our results suggests two competing hypotheses on the evolution of drainage density in mature catchments. One is that as catchments continue to age, the hydrologically active channels retreat because less recharge leads to lower average aquifer levels and less baseflow. The other hypothesis is that the active channels do not undergo much surface dissection after the catchments reach maturity. © 2016 Author(s).

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