Biology subjects

Katoh, T. K.

Publications and source records attributed to Katoh, T. K..

4 recordsLinked to original sources

bioRxiv2025

Disentangling sex-ratio meiotic drive in Drosophila a century after its original discovery

Sex ratio is distorted when selfish elements linked to the sex chromosome cause meiotic drive. Since the first report on the drive in Drosophila obscura in 1928, this phenomenon has been reported in diverse taxa. However, the molecular and evolutionary mechanisms of the drive have remained largely elusive, even in D. obscura. We therefore reinvestigated this original example by comparing D. obscura strains with and without distortion (SR and ST strains, respectively). Crossing experiments indicated the presence of a driver on the X chromosome and predicted the existence of a suppressor. Using comparative genomics, we identified an X-linked gene, Gcna, as a candidate driver; the region encoding the SprT-like domain of this gene was massively duplicated only in the SR genome. We further identified a candidate suppressor, miR-9c, that interacted with Gcna in the SR strain but not with that in the ST strain. Gcna with amplified SprT-like domains likely targets transient TOP2-DPC on the Y chromosome and may disrupt or kill sperm harboring the Y chromosome; this was supported by the small number of sperm in the SR strain. Our findings demonstrate an evolutionary arms race between driver and suppressor genes in a longstanding example of sex-ratio meiotic drive.

evolutionary biology↗

bioRxiv2022

Secondary reversion to sexual monomorphism associated with tissue-specific loss of doublesex expression

Animal evolution is characterized by frequent turnover of sexually dimorphic traits - new sex- specific characters are gained, and some ancestral sex-specific characters are lost, in many lineages. In insects, sexual differentiation is predominantly cell-autonomous and depends on the expression of the doublesex (dsx) transcription factor. In most cases, cells that transcribe dsx have the potential to undergo sex-specific differentiation, while those that lack dsx expression do not. Consistent with this mode of development, comparative research has shown that the origin of new sex-specific traits can be associated with the origin of new spatial domains of dsx expression. In this report, we examine the opposite situation - a secondary loss of the sex comb, a male-specific grasping structure that develops on the front legs of some drosophilid species. We show that, while the origin of the sex comb is linked to an evolutionary gain of dsx expression in the leg, sex comb loss in a newly identified species of Lordiphosa (Drosophilidae) is associated with a secondary loss of dsx expression. We discuss how the developmental control of sexual dimorphism affects the mechanisms by which sex-specific traits can evolve.

evolutionary biology↗

bioRxiv2021

Revision of the genus Dichaetophora Duda (Diptera: Drosophilidae), part I: DNA bar-coding and molecular phylogenetic reconstruction

The genus Dichaetophora is currently comprised of 67 formally described species assigned into five species groups, i.e., agbo, tenuicauda, acutissima, sinensis and trilobita. In the present study, we challenged to delimit species from a huge amount of samples of Dichaetophora and allied taxa (the genus Mulgravea and the subgenus Dudaica of Drosophila) collected from a wide range of the Oriental and east Palearctic regions. We first sorted all specimens into morpho-species, which were tentatively classified into the species groups of Dichaetophora, Mulgravea and Dudaica based on the morphological diagnoses for these supraspecific taxa. Then, we selected representative specimen(s) for each morpho-species and subjected them to barcoding of COI (the cytochrome c oxidase subunit I gene) sequences. The applied ABGD (automatic barcode gap discovery) algorithm estimated a total of 222 MOTUs (molecular operational taxonomic units). Although most of the morpho-species were recognized as individual MOTUs, some others were divided into multiple MOTUs or combined into a single MOTU, suggesting the existence of cryptic sibling species, subspecies or intraspecific genetic varieties. Out of the 222 MOTUs, 88 representing the supraspecific taxa of Dichaetophora, Mulgravea and Dudaica were selected, along with 33 species from major genera and subgenera of Drosophila in the tribe Drosophilini, as in-group (four species from the tribe Colocasiomyini as out-group) for phylogenetic reconstruction. We analyzed a dataset of concatenated nucleotide sequences of 12 nuclear gene markers by the maximum likelihood and Bayesian inference methods. As a result, the three focal taxa (i.e., Dichaetophora, Mulgravea and Dudaica) formed a clade, which we called the "pan-Dichaetophora". Within this large clade, the agbo, tenuicauda, sinensis and trilobita groups of Dichaetophora, Mulgravea and Dudaica were recovered as monophyletic groups, but Dichaetophora and its acutissima group were regarded as paraphyletic. In addition, two clusters were recognized among ungrouped MOTUs of Dichaetophora. Thus, the present study has uncovered some problems in the taxonomy of the pan-Dichaetophora. Solving such problems will be challenged in Part II of this serial work.

zoology↗

bioRxiv2020

Highly contiguous assemblies of 101 drosophilid genomes

Over 100 years of studies in Drosophila melanogaster and related species in the genus Drosophila have facilitated key discoveries in genetics, genomics, and evolution. While high-quality genome assemblies exist for several species in this group, they only encompass a small fraction of the genus. Recent advances in long read sequencing allow high quality genome assemblies for tens or even hundreds of species to be generated. Here, we utilize Oxford Nanopore sequencing to build an open community resource of high-quality assemblies for 101 lines of 95 drosophilid species encompassing 14 species groups and 35 sub-groups with an average contig N50 of 10.5 Mb and greater than 97% BUSCO completeness in 97/101 assemblies. These assemblies, along with detailed wet lab protocol and assembly pipelines, are released as a public resource and will serve as a starting point for addressing broad questions of genetics, ecology, and evolution within this key group.

evolutionary biology↗