Biology subjects

Futahashi, R.

Publications and source records attributed to Futahashi, R..

5 recordsLinked to original sources

bioRxiv2025

Acquisition and repeated alteration of (TTGGG)n telomeric repeats in Odonata (dragonflies and damselflies)

Chromosome ends of most eukaryotes are composed of simple telomeric repeats. For arthropods, TTAGG pentanucleotide repeats, (TTAGG)n has been considered as the ancestral telomeric repeat. However, in the order Odonata, the earliest diverged group in insects that contains dragonflies and damselflies, (TTAGG)n signal has been almost undetectable in most examined species. Here, we report a unique pentanucleotide repeat (TTGGG)n as the typical telomeric repeat sequence for Odonata (dragonflies and damselflies). Based on genomic information from ten Odonata species, (TTGGG)n was considered the most likely candidate for telomeric repeat sequences. By fluorescence in situ hybridization (FISH) using 12 Odonata species, clear (TTGGG)n signals were detected at the chromosome ends in both dragonflies and damselflies. By Southern hybridization using 63 Odonata species, strong (TTGGG)n signals were detected from the majority of species covering all three suborders of Odonata, indicating that the telomeric repeat of the common ancestor of extant Odonata is (TTGGG)n. Notably, there were a few Odonata species in which (TTGGG)n signals were faint or absent, suggesting that the telomeric repeat sequence has repeatedly diverged in Odonata, even within genera such as Sympetrum. We also identified telomerase genes in both dragonflies and damselflies, and in some species, more than two telomerase genes are suggested to be present. Overall, this study demonstrates the ancestral acquisition of novel telomeric repeats and their repeated alteration in Odonata.

cell biology↗

bioRxiv2023

Hundreds of antimicrobial peptides create a selective barrier for insect gut symbionts

The spatial organization of gut microbiota is crucial for the functioning of the gut ecosystem, although the mechanisms that organize gut bacterial communities in microhabitats are only partially understood. The gut of the insect Riptortus pedestris has a characteristic microbiota biogeography with a multispecies community in the anterior midgut and a mono-specific bacterial population in the posterior midgut. We show that the posterior midgut region produces massively hundreds of specific antimicrobial peptides (AMPs), the Crypt-specific Cysteine-Rich peptides (CCRs) that have membrane-damaging antimicrobial activity against diverse bacteria but posterior midgut symbionts have elevated resistance. We determined by transposon-sequencing the genetic repertoire in the symbiont Caballeronia insecticola to manage CCR stress, identifying different independent pathways, including novel AMP-resistance pathways unrelated to known membrane homeostasis functions as well as cell envelope functions. Mutants in the corresponding genes have reduced capacity to colonize the posterior midgut, demonstrating that CCRs create a selective barrier and resistance is crucial in gut symbionts. Moreover, once established in the gut, the bacteria differentiate into a CCR-sensitive state, suggesting a second function of the CCR peptide arsenal in protecting the gut epithelia or mediating metabolic exchanges between the host and the gut symbionts. Our study highlights the evolution of an extreme diverse AMP family that contributes to establish and control the gut microbiota.

microbiology↗

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↗

bioRxiv2021

Mutations in a β-group of solute carrier gene are responsible for egg and eye coloration of the brown egg 4 (b-4) mutant in the silkworm, Bombyx mori

The brown egg 4 (b-4) is a recessive mutant in the silkworm (Bombyx mori), whose egg and adult compound eyes exhibit a reddish-brown color instead of normal purple and black, respectively. By double digest restriction-site associated DNA sequencing (ddRAD-seq) analysis, we narrowed down a region linked to the b-4 phenotype to approximately 1.1 Mb that contains 69 predicted gene models. RNA-seq analysis in a b-4 strain indicated that one of the candidate genes had a different transcription start site, which generates a short open reading frame. We also found that exon skipping was induced in the same gene due to an insertion of a transposable element in other two b-4 mutant strains. This gene encoded a putative amino acid transporter that belongs to the {beta}-group of solute carrier (SLC) family and is orthologous to Drosophila eye color mutant gene, mahogany (mah). Accordingly, we named this gene Bmmah. We performed CRISPR/Cas9-mediated gene knockout targeting Bmmah. Several adult moths in generation 0 (G0) had totally or partially reddish-brown compound eyes. We also established three Bmmah knockout strains, all of which exhibit reddish-brown eggs and adult compound eyes. Furthermore, eggs from complementation crosses between the b-4 mutants and the Bmmah knockout mutants also exhibited reddish-brown color, which was similar to the b-4 mutant eggs, indicating that Bmmah is responsible for the b-4 phenotypes. HighlightO_LIResponsible region for the brown egg 4 (b-4) mutation was narrowed down by double digest restriction-site associated DNA sequencing (ddRAD-seq). C_LIO_LIThe gene structure was disrupted in one of the candidate genes, Bombyx mori mahogany (Bmmah), in the b-4 mutant strains. C_LIO_LICRISPR/Cas9-mediated gene knockout and complementation test confirmed that the Bmmah is responsible for the b-4 phenotypes. C_LIO_LIThe Bmmah encoded a putative amino acid transporter that belongs to the {beta}-group of solute carrier family. C_LIO_LIThe Bmmah gene is essential for normal colorization of eggs, compound eyes, and ganglions. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/436376v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@10d1d56org.highwire.dtl.DTLVardef@12df5org.highwire.dtl.DTLVardef@1703701org.highwire.dtl.DTLVardef@2b5bcf_HPS_FORMAT_FIGEXP M_FIG C_FIG

genetics↗

bioRxiv2020

Involvement of the doublesex gene in body color masculinization of the blue-tailed damselfly, Ischnura senegalensis

Odonata (dragonflies and damselflies) display remarkable color pattern diversity including sexual dimorphism and intrasexual polymorphism. We previously found that expression of a sex-determining transcription factor, the doublesex (dsx) gene, is associated with female color polymorphism (gynomorph for female-specific color and andromorph for male mimicking color) in the blue-tailed damselfly, Ischnura senegalensis. Here we investigate the function of dsx gene on thoracic coloration by electroporation-mediated RNA interference (RNAi). RNAi of the dsx common region changed color patterns of males and andromorphic females to patterns of gynomorphic females. Further, gynomorphic color pattern was not affected by dsx RNAi. The long isoform of dsx RNAi produced no effects, suggesting that the short isoform of dsx is important for body color masculinization in both males and andromorphic females. Expression pattern changes were also examined in five genes with different expression levels between sexes and female morphs. Among these genes are two melanin suppressing genes, black and ebony, that were upregulated in the dsx-RNAi region compared to a control region. Upregulation coincides with a gynomorphic orange color instead of the black stripe observed in males and andromorphic females. dsx may regulate male color differentiation by suppressing black and ebony in the thoracic region of I. senegalensis. Results add to the understanding of molecular mechanisms underlying the evolution of female polymorphism in Odonata.

genetics↗