||Kyaw, H.W.W., Tsuchiya, K., Matsumoto, M., Kurose, D., Iiyama, K., Horita, M., and Furuya, N., Properties of potato strains of Ralstonia solanacearum in Myanmar, 平成30年度日本植物病理学会, 2018.03.
||Htet Wai Wai Kyaw, Masaru Matsumoto, Kazuhiro Iiyama, Mitsuo Horita, Daisuke Kurose, Kenichi Tsuchiya, Naruto Furuya, Characterization of Ralstonia solanacearum strains causing bacterial wilt of solanaceous crops in Myanmar, AFELiSA 2017 International Symposium on Agricultural, Food, Environmental and Life Sciences in Asia, 2017 (The 14th International Joint Symposium between Japan and Korea), 2017.11.
||Kyaw, H.W.W., Matsumoto, M., Kurose, D., Iiyama, K., Horita, M., Tsuchiya, K., Furuya, N., Genetic diversity of Myanmar strains of Ralstonia solanacearum, 平成29年度日本植物病理学会, 2017.04.
||Erika Taira, Kazuhiro Iiyama, Jae Man Lee, Takahiro Kusakabe, Chisa Yasunaga-Aoki, Lipopolysaccharide contributes to the virulence of Serratia liquefaciens against Bombyx mori, The 4th Asia-Pacific Congress of Sericulture and Insect Biotechnology (APSERI 2015), 2015.04.
||Shota Fukui, Chisa Yasunaga-Aoki, Takashi Matsuyama, Kazuhiro Iiyama, Study on in vitro excystation of Farinocystis sp. isolated from the West Indian sweet potato weevil, Euscepes postfasciatus, The 4th Asia-Pacific Congress of Sericulture and Insect Biotechnology (APSERI 2015), 2015.04.
||Shota Fukui, Chisa Yasunaga-Aoki, Takashi Matsuyama, Kazuhiro Iiyama, Study on intestinal factors affecting excystation of Farinocystis sp. in the West Indian sweet potato weevil, Euscepes postfasciatus, International Symposium on Basic and Applied Research on Sericulture and Insect Sciences, Collaboratively Organized by Kyushu Branch of Japanese Society of Sericultural Science, Japan and College of Agriculture and Life Sciences, Kyungpook National Univer, 2015.04.
||Erika Taira, Kazuhiro Iiyama, Jae Man Lee, Takahiro Kusakabe, Chisa Yasunaga-Aoki, Sensitivity to oxidative stress in lipopolysaccharide mutants of Serratia liquefaciens, International Symposium on Basic and Applied Research on Sericulture and Insect Sciences, Collaboratively Organized by Kyushu Branch of Japanese Society of Sericultural Science, Japan and College of Agriculture and Life Sciences, Kyungpook National Univer, 2015.04.
||Erika Taira, Kazuhiro Iiyama, Jae Man Lee, Takahiro Kusakabe, Chisa Yasunaga-Aoki, Virulence of Serratia liquefaciens against Bombix mori, International Symposium on Agriculture, Forestry, Environment and Life Sciences in Asia, 2014, 2014.10, Serratia spp. are Gram-negative bacteria of the family Enterobacteriaceae. Serratia spp. are ubiquitous environmental bacteria, and they infect a wide range of species from animals to plants. Unfortunately, Serratia spp. have been reported to kill useful insects, such as the silkworm, Bombyx mori, and the honeybee, Apis mellifera. Therefore, in order to protect these useful insects from diseases caused by Serratia spp., it is important to elucidate their pathogeneses. In our previous work, S. liquefaciens isolated from an antlion larva was highly virulent against the silkworm. Since the virulence of S. liquefaciens remains poorly understood, a comprehensive analysis using transposon-induced mutants was carried out to investigate its virulence against the silkworm in the present study. Firstly, a transposon insertion library of S. liquefaciens FK01 was constructed. Subsequently, 1,200 transconjugants were injected into the hemocoel of silkworm larvae. Then, four transposon mutants showing a reduced virulence were screened. Southern blot analysis confirmed the insertion of transposons at single sites in the transconjugants. Sequences flanking both sides of the transposons indicated that they were inserted into the lipopolysaccharide (LPS) biosynthesis genes in these transconjugants. These results suggest that LPS markedly contributes to the virulence of S. liquefaciens against the silkworm. The role of LPS in the virulence of S. liquefaciens against the silkworm remains to be determined..
||Oumi Nishi, Kazuhiro Iiyama, Chisa Yasunaga-Aoki, Susumu Shimizu, Comparative virulence analysis of entomopathogenic fungus Metarhizium spp. in different ambient temperature conditions., International Symposium on Agricultural, Food, Environmental and Life Sciences in Asia, 2013, 2013.11.
||Pseudomonas aeruginosa is a Gram-negative, rod shaped bacterium and human opportunistic pathogen. Since several strains of the P. aeruginosa infect plants, nematodes and insects, some organisms have been used as model hosts of P. aeruginosa infection. To use silkworm, Bombyx mori, as a model host, it is important to compare the bacterial virulence strategies between the different hosts, mammal and B. mori.
We created the mutants of GacS-GacA two component system (gacA), pyocyanin production (phzM, phzS), superoxide dismutase (SOD) production (sodM, sodB, sodM sodB) and nucleotide excision repair (NER) mechanism (uvrC) originated from P. aeruginosa PAO1. Among these genes, gacA, sodB phzM and phzS have been reported to be important in the virulence to mammalian hosts. Gene disruption in each mutant was confirmed by Southern hybridization and change of phenotypic characteristics (pyocyanin production, SOD activity and UV sensitivity). Inoculation test demonstrated that gacA, phzM, phzS mutants had the same level of virulence in comparison with the parent strain, PAO1. Whereas, sodB, sodM sodB and uvrC mutants showed reduced virulence. In addition, the virulence of the mutants was restored by the complementation of the corresponding genes in trans. These results suggested that the importance of these virulence factors depended on the host species, but that of the survival factors were common in P. aeruginosa..
||It is known that the GacS/GacA two-component system is important for the virulence of Pseudomonas aeruginosa in invertebrate and vertebrate hosts and in plants. In this study, the gacA nonpolar mutant C2 and polar mutant C3 were generated and inoculated into Bombyx mori. The polar mutants showed reduced virulence, whereas no significant difference was observed between the gacA nonpolar mutant and wild type strain with respect to the ability to kill B. mori larvae. This suggests that the reduced virulence was due to a polar effect of the insertions, rather than to the lack of the gacA gene product.
In the genome, the gacA gene is directly followed by a uvrC gene. To clarify the importance of uvrC to virulence, the uvrC mutant strain UC was constructed. UC strains were assessed for the production of virulence factors (pyocyanin, pyoverdine, elastase and total protease) in comparison to UC strains. No difference was observed between PAO1 (parent strain) and UC strains, suggesting that the mutation of uvrC had no effect on the production of these virulence factors.
UvrC is an endonuclease involved in NER, which is one of the excision repair systems. We tested the survival of UC strains exposed to cisplatin or UV. The survival rate of UC (pBBR1MCS2) after cisplatin or UV treatment was clearly lower than that of PAO1 (pBBR1MCS2).
To investigate the influence of uvrC on virulence of hemocoel infection, UC strains were injected into B. mori. UC was shown to be less virulent than PAO1. This result suggests that not gacA rather than uvrC is necessary for the full virulence of P. aeruginosa PAO1 to in B. mori..