Biology subjects

Kuwazaki, S.

Publications and source records attributed to Kuwazaki, S..

5 recordsLinked to original sources

bioRxiv2023

A major endogenous glycosidase mediating quercetin uptake in Bombyx mori

Quercetin is a common plant flavonoid that is involved in herbivore-plant interactions. Mulberry silkworms (domestic silkworm, Bombyx mori, and wild silkworm, Bombyx mandarina) uptake quercetin from mulberry leaves and accumulate the metabolites in the cocoon, thereby improving its protective properties. Here we identified and characterized a glycosidase, named LPH-like quercetin glycoside hydrolase 1 (LQGH1), that initiates quercetin metabolism in the domestic silkworm. LQGH1 is expressed in the midgut where it mediates quercetin uptake by deglycosylating the three most common quercetin glycosides present in mulberry leaf: rutin, quercetin-3-O-malonyl-glucoside, quercetin-3-O-glucoside. Despite being located in an unequal crossing-over hotspot, LQGH1 is conserved in some species in clade Macroheterocera, including the wild silkworm, indicating the adaptive significance of quercetin uptake. LQGH1 is important also in breeding: defective mutations of LQGH1, which result in discoloration of the cocoon and increased silk yield, are homozygously conserved in 27 of the 32 Japanese white-cocoon domestic silkworm strains and 12 of the 30 Chinese ones we investigated.

genetics↗

bioRxiv2023

Genome assembly reconstruction of the Japanese honey bee, Apis cerana japonica (Hymenoptera: Apidae), using homology-based assembly and nanopore long-reads

Honey bees are important for agriculture (e.g., pollination and honey production). Additionally, honey bees are an important insect model species, especially as model social insects. The Japanese honey bee, Apis cerana japonica (a subspecies of the Asian honey bee, Apis cerana), is a Japanese domestic honey bee, which has several subspecies-specific traits. We previously constructed the draft genome sequence data of A. cerana japonica, but it needed to be improved considering the use of the genome sequence data for genome structural analysis and repetitive region analysis, as well as the availability of chromosome-level genome data of A. mellifera and A. cerana. In this study, we constructed the improved A. cerana japonica genome data and new gene set data with functional annotations. The constructed genome data, including 16 pseudochromosomes, was found to be highly contiguous and complete, and the gene set data covered most of the core genes in the BUSCO database. Thus, the constructed genome and gene set data have become more suitable as the reference data of A. cerana japonica.

genomics↗

bioRxiv2023

A novel monocarboxylate transporter involved in 3-hydroxykynurenine transport for ommochrome coloration

Ommochromes are widespread pigments in invertebrates utilized for screening pigments in compound eyes and for reddish coloration in epidermis and wings. Ommochromes are derived from 3-hydroxykynurenine (3OHK), which is incorporated into cells from hemolymph or synthesized from tryptophan within cells. While the synthetic pathway from tryptophan to 3OHK has been well characterized, the gene responsible for cellular uptake of 3OHK has been poorly understood. In the silkworm Bombyx mori, adult compound eyes and eggs contain a mixture of ommochrome pigments. By using positional cloning method, we found that a novel monocarboxylate transporter, 3-hydroxykynurenine transporter (3OHKT), is responsible for the recessive mutant maternal brown of Tsujita (b-t) of B. mori. In b-t mutant, the color of the eggs is light brown, whereas the color of the compound eyes is normal, and we identified a 2-kb deletion in 3OHKT gene. TALEN-mediated knockout of 3OHKT gene produced the same coloration phenotype as b-t mutant, and the complementation test between b-t mutant and 3OHKT knockout strain proved that 3OHKT is responsible for b-t phenotype. 3OHKT protein was localized in the cellular membrane, and LC-MS analysis indicated that the uptake of 3OHK from hemolymph into the ovary was suppressed in the b-t mutant. Moreover, we confirmed that 3OHKT gene is specifically expressed at the reddish region and the time of pigmentation in the pupal wing of nymphalid butterflies. RNA interference of 3OHKT prevented reddish pigmentation in wings, highlighting its general involvement in ommochrome-based pigmentation other than compound eyes. SignificanceOmmochromes are widely distributed pigments in invertebrates and are synthesized from intracellular tryptophan or 3-hydroxykynurenine (3OHK). Ommochrome-based red markings on butterfly wings are often used for sexual selection, warning colors and mimicry. Most genes involved in the ommochrome synthesis pathway have been elucidated from analyses of eye color mutants in Drosophila. However, this study reveals that the ommochrome synthesis pathway has a different genetic repertoire depending on the tissues, and that the novel monocarboxylate transporter identified in this study has a major role in ommochrome pigmentation other than in compound eyes. In particular, our results suggest that classical ommochrome-related genes are rarely involved in the wing pigmentation of the nymphalid butterflies.

genetics↗

bioRxiv2022

Highly accurate genome assembly of an improved high-yielding silkworm strain, Nichi01

The silkworm (Bombyx mori) is an important lepidopteran model insect, and an industrial domestic animal traditionally used for silk production. Here, we report the genome assembly of an improved Japanese strain Nichi01, in which the cocoon yield is comparable to that of commercial silkworm strains. The integration of PacBio Sequel II long-read and ddRAD-seq-based high-density genetic linkage map achieved the highest quality genome assembly of silkworms to date; 22 of the 28 pseudomolecules contained telomeric repeats at both ends, and only four gaps were present in the assembly. A total of 452 Mbp of the assembly with an N50 of 16.614 Mbp covered 99.3% of the complete orthologs of the Arthropod core genes. Although the genome sequence of Nichi01 and that of the previously reported low-yielding tropical strain p50T assured their accuracy in most regions, we corrected several regions, misassembled in p50T, in our assembly. A total of 18,397 proteins were predicted using over 95 Gb of mRNA-seq derived from 10 different organs, covering 96.9% of the complete orthologs of the Arthropod core genes. The final assembly and annotation files are available in KAIKObase (https://kaikobase.dna.affrc.go.jp/index.html) along with a genome browser and BLAST searching service, which would facilitate further studies and the breeding of silkworms and other insects.

genomics↗

bioRxiv2017

Master manipulation continued: feminizing Wolbachia endosymbiont distorts sex chromosome inheritance

Genomes are vulnerable to selfish genetic elements that enhance their own transmission often at the expense of host fitness. Examples are cytoplasmic elements such as maternally inherited bacteria that cause feminization, male-killing, parthenogenesis and cytoplasmic incompatibility. We demonstrate, for the first time, that segregation distortion, a phenomenon so far seen only for nuclear genetic elements, can also be caused by a cytoplasmic element, the ubiquitous endosymbiotic bacterium Wolbachia. For Eurema mandarina butterfly lineages with a Z0 sex chromosome constitution, we provide direct and conclusive evidence that Wolbachia induces production of all-female progeny by a dual role: the compensation for the female-determining function that is absent in Z0 lineages (feminization) and the prevention of maternal sex chromosome inheritance to offspring as a specific type of segregation distortion. Therefore, our findings highlight that both sex determination and chromosome inheritance -- crucially important developmental processes of higher eukaryotes -- can be manipulated by cytoplasmic parasites.

evolutionary biology↗