Browsing by Author "Fukatsu, Takema"

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Natsumushi: Image measuring software for entomological studies
(2018-09-01)
Tanahashi, Masahiko
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Fukatsu, Takema
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應用化學系
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Department of Applied Chemistry
Natsumushi is a free image analysis software that offers easy handling and quick measurement, designed especially for entomologists as the main users. The software enables measurement of: (i) color features of a specific region; (ii) area size; (iii) length of simple lines or polylines; and (iv) number of points or their x-y coordinates. Users can specify the region for measurement either manually or automatically by using image thresholding operations.
Recurrent symbiont recruitment from fungal parasites in cicadas
(2018-06-26)
Matsuura, Yu
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Moriyama, Minoru
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Lukasik, Piotr
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Vanderpool, Dan
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Tanahashi, Masahiko
Diverse insects are associated with ancient bacterial symbionts, whose genomes have often suffered drastic reduction and degeneration. In extreme cases, such symbiont genomes seem almost unable to sustain the basic cellular functioning, which comprises an open question in the evolution of symbiosis. Here, we report an insect group wherein an ancient symbiont lineage suffering massive genome erosion has experienced recurrent extinction and replacement by host-associated pathogenic microbes. Cicadas are associated with the ancient bacterial co-obligate symbionts Sulcia and Hodgkinia, whose streamlined genomes are specialized for synthesizing essential amino acids, thereby enabling the host to live on plant sap. However, our inspection of 24 Japanese cicada species revealed that while all species possessed Sulcia, only nine species retained Hodgkinia, and their genomes exhibited substantial structural instability. The remaining 15 species lacked Hodgkinia and instead harbored yeastlike fungal symbionts. Detailed phylogenetic analyses uncovered repeated Hodgkinia-fungus and fungus-fungus replacements in cicadas. The fungal symbionts were phylogenetically intermingled with cicada-parasitizing Ophiocordyceps fungi, identifying entomopathogenic origins of the fungal symbionts. Most fungal symbionts of cicadas were uncultivable, but the fungal symbiont of Meimuna opalifera was cultivable, possibly because it is at an early stage of fungal symbiont replacement. Genome sequencing of the fungal symbiont revealed its metabolic versatility, presumably capable of synthesizing almost all amino acids, vitamins, and other metabolites, which is more than sufficient to compensate for the Hodgkinia loss. These findings highlight a straightforward ecological and evolutionary connection between parasitism and symbiosis, which may provide an evolutionary trajectory to renovate deteriorated ancient symbiosis via pathogen domestication.
Specificity and genetic diversity of xylose-fermenting Scheffersomyces yeasts associated with small blue stag beetles of the genus Platycerus in East Asia
(2017-01-01)
Tanahashi, Masahiko
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Kim, Jong-Kuk
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Watanabe, Kana
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Fukatsu, Takema
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Kubota, Kohei
Among insect-fungus relationships, xylose-fermenting Scheffersomyces yeasts are well known for their potential in utilizing wood hemicelluloses and their association with various wood-feeding insects. However, their specificity to host insects or strain-level diversity within host species has not been clearly elucidated. In the insect family Lucanidae, larvae usually feed on decaying wood, and adult females consistently possess a fungus-storage organ, called the mycangium, near the abdominal tip. Here the authors investigated host-symbiont relationships between Scheffersomyces yeast symbionts and small blue stag beetles of the genus Platycerus (Coleoptera: Lucanidae) in East Asia by using intergenic spacer (IGS) region as a genetic marker. All yeast strains isolated from the female mycangiumof three Platycerus species, P. hongwonpyoi from Korea and P. acuticollis and P. delicatulus from Japan, were allied to Scheffersomyces segobiensis based on the sequences of the nrDNA 26S and internal transcribed spacer (ITS), in which no sequence difference was observed among those strains. However, IGS regions showed clear genetic differentiation within the yeast symbionts of P. hongwonpyoi, as well as between those of Korean and Japanese Platycerus species. In the IGS sequences, nucleotide substitutions were mainly distributed in the whole stretch of IGS1 and the anterior half of IGS2, whereas nucleotide gaps were localized at IGS1 and the middle of IGS2. Despite the conserved association between the Platycerus beetles and the specific strains of S. segobiensis in East Asia, geophylogenetic divergence patterns of the yeast symbionts were not concordant with those of the insect hosts.