Biology subjects

Abe, J.

Publications and source records attributed to Abe, J..

11 recordsLinked to original sources

bioRxiv2026

Females do not avoid but prefer superparasitism in the parasitoid wasp Melittobia australica

To reduce competition over limited resources, organisms often avoid resources already used by others. In parasitoid insects, females are generally expected to avoid parasitizing hosts already parasitized by other females, called superparasitism, and this prediction has been broadly supported across numerous species. However, in the parasitoid wasp Melittobia australica, multiple females were observed ovipositing on the same host despite the presence of nearby unparasitized hosts in the field. In this study, we first analysed field data using randomization tests, and found that females strongly aggregated on particular hosts rather than distributing randomly across hosts. We then conducted laboratory experiments to examine (1) whether this aggregation reflects an active preference for superparasitism and (2) whether such behaviour could improve parasitism efficiency. A choice experiment, in which females were provided with a parasitized and an unparasitized host, showed that females preferred superparasitism when hosts were non-diapausing. This result indicates that females of M. australica not only engage in superparasitism, but actively prefer parasitized hosts. Another experiment, in which varying numbers of females were allowed to oviposit on a host, found that offspring number per female decreased with increasing female number on diapausing hosts, whereas it remained constant irrespective of female number on non-diapausing hosts. This host-dependent result suggests that multiple females can more effectively paralyze vigorous non-diapausing hosts, thereby offsetting the negative effects of offspring competition. As Melittobia females are likely to attack non-diapausing hosts in most cases in the field, including those in the present study, this benefit of parasitism by multiple females may help explain their preference for superparasitism, in contrast to many other parasitoid species.

animal behavior and cognition↗

bioRxiv2024

A lymphoid tissue chemokine checkpoint prevents loss of CD8+ T cell functionality

The generation of effector CD8+ T cells (TEFF) requires activation of naive CD8+ T cells (TN) by dendritic cells (DCs) within lymphoid tissue. To date, it remains elusive how the duration of TN-DC interactions and integration of activation signals are controlled in vivo. Here, we report that lymphoid stroma-secreted ligands for CCR7 constrained interaction duration by gradually inducing CD8+ T cell release from DCs. At late time points of interactions, CCR7 ligands repositioned the F-actin-promoting factor DOCK2 away from the DC interface to enable CD8+ T cell detachment, proliferation onset and acquisition of cytotoxicity. Lack of CCR7 signaling, as during ex vivo activation or in chronically inflamed lymphoid tissue, caused sustained T cell-DC interactions, and generated dysfunctional TEFF with high expression of inhibitory receptors, impaired antimicrobial activity, and poor recall responses. In sum, our findings uncover that lymphoid stromal chemokines act as built-in "disruptors" of T cell-DC interactions for long-term preservation of TEFF functionality.

immunology↗

bioRxiv2024

High microsatellite but no mitochondrial DNA variation in an invasive Japanese mainland population of the parasitoid wasp Melittobia sosui

Theory predicts that bottleneck events reduce genetic diversity in invasive populations. The parasitoid wasp Melittobia sosui was only identified in the subtropical area of Japanese south islands and Taiwan, but recently found also in the temperate area of the Japanese mainland. The species may expand their distribution northward due to factors such as recent global warming. We investigated population genetics in both the native and invasive areas using mitochondrial and nuclear microsatellite DNA. As expected, there was mitochondrial variation in the native area, but not in the invasive area, which only had one haplotype. However, the two areas had a similar level of microsatellite variation, with averagely 43% and 38% alleles uniquely found in the native and invasive populations, respectively. The difference of genetic variation between mitochondrial and microsatellite DNA in the invasive populations may be explained by the faster mutation rate of microsatellites, as well as the population structure of Melittobia, in which subdivided small inbreeding lineages may facilitate the accumulation of mutations. The high proportion of private alleles suggests that the mainland population diverged from the native populations at least 100 years ago, ruling out the possibility that the mainland population was established recently. Instead, the present study suggests that M. sosui might have already existed in the mainland but with a low frequency, or the mainland population was derived from a third population which diverged from the native populations over 100 years ago.

ecology↗

bioRxiv2021

Naive and in vitro-activated primary mouse CD8+ T cells retain in vivo immune responsiveness after electroporation-based CRISPR/Cas9 genetic engineering

CRISPR/Cas9 technology has revolutionized genetic engineering of primary cells. Although its use is gaining momentum in studies on CD8+ T cell biology, it remains elusive to what extent CRISPR/Cas9 affects in vivo function of CD8+ T cells. Here, we optimized nucleofection-based CRISPR/Cas9 genetic engineering of naive and in vitro-activated primary mouse CD8+ T cells and tested their in vivo immune responses. Nucleofection of naive CD8+ T cells preserved their in vivo antiviral immune responsiveness to an extent that is indistinguishable from non-nucleofected cells, whereas in vitro activation of CD8+ T cells prior to nucleofection led to slightly impaired expansion/survival. Of note, different target proteins displayed distinct decay rates after gene editing. This is in stark contrast to a comparable period of time required to complete gene inactivation. Thus, for optimal experimental design, it is crucial to determine the kinetics of the loss of target gene product to adapt incubation period after gene editing. In sum, nucleofection-based CRISPR/Cas9 genome editing achieves efficient and rapid generation of mutant CD8+ T cells without imposing detrimental constraints on their in vivo functions.

immunology↗

bioRxiv2021

Multi-tier mechanics control stromal adaptations in swelling lymph nodes

Lymph nodes (LNs) comprise two main structural elements: Fibroblastic reticular cells (FRCs) that form dedicated niches for immune cell interaction and capsular fibroblasts that build a shell around the organ. While LNs are fairly stable in size during homeostatic conditions, immunological challenge causes more than 10-fold increase in size within only a few days. How a solid organ can accommodate such extreme volumetric changes is poorly understood. Here, we characterize the biomechanics of LN swelling on the cellular and organ scale. We identify lymphocyte trapping by influx and proliferation as drivers of an outward pressure force, causing FRCs and their associated conduits to stretch. After an initial phase of relaxation, FRCs sense the resulting strain via cell matrix adhesions, which coordinates local growth and remodeling of the stromal network. While the expanded FRC network adopts its typical configuration, a massive fibrotic reaction of the organ capsule sets in and counters further organ expansion. Thus, different fibroblast populations mechanically control LN swelling in a multi-tier fashion.

immunology↗

bioRxiv2020

Solving the sex ratio scandal in Melittobia wasps

The scandalous sex ratio behaviour of Melittobia wasps has long posed one of the greatest problems for the field of sex allocation. In contrast to the predictions of theory, and the behaviour of numerous other organisms, laboratory experiments have found that Melittobia females do not produce less female-biased offspring sex ratios when more females lay eggs on a patch. We resolve this scandal, by showing that, in nature, females of M. australica have sophisticated sex ratio behaviour, where their strategy also depends upon whether they have dispersed from the patch where they emerged. When females have not dispersed, they will be laying eggs with close relatives, which keeps local mate competition high, even with multiple females, and so they are selected to produce consistently female-biased sex ratios. Laboratory experiments mimic these conditions. In contrast, when females disperse, they will be interacting with non-relatives, and so they adjust their sex ratio depending upon the number of females laying eggs. Consequently, females appear to use dispersal status as an indirect cue of relatedness, and whether they should adjust their sex ratio in response to the number of females laying eggs on the patch.

evolutionary biology↗

bioRxiv2020

CD8+ T cell priming in oral mucosa-draining lymph nodes supports systemic immunity

The gastrointestinal (GI) tract constitutes an essential barrier against ingested pathogens. While immune reactions are well-studied in the lower GI tract, it remains unclear how adaptive immune responses are initiated during microbial challenge of the oral mucosa, the primary site of pathogen encounter in the upper GI tract. Here, we identify mandibular lymph nodes (mandLN) as sentinel lymphoid organs that collect orally administered Listeria monocytogenes (Lm), leading to local CD8+ T cell activation. In contrast to CD8+ T effector cells (TEFF) generated in mesenteric lymph nodes, mandLN CD8+ TEFF lacked a gut-seeking phenotype but contributed to systemic host protection. Accordingly, mandLN stromal and dendritic cells expressed low levels of enzymes required for gut homing imprinting. Our findings extend the concept of regional specialization of immune responses along the length of the GI tract, with mandLN acting as oral lymph-draining counterparts of intestinal lymph-draining LN of the lower GI tract. SummaryListeria monocytogenes ingestion leads to priming of cytotoxic T cells in oral mucosa draining mandibular lymph nodes, which contribute to systemic host protection.

immunology↗

bioRxiv2020

Evolution of nuptial gifts and its coevolutionary dynamics with "masculine" female traits for multiple mating

Many male animals donate nutritive materials during courtship or mating to their female mates. Donation of large-sized gifts, though costly to prepare, can result in increased sperm transfer during mating and delayed remating of the females, resulting in a higher paternity Nuptial gifting sometimes causes severe female-female competition for obtaining gifts (i.e., sex-role reversal in mate competition) and female polyandry, changing the intensity of sperm competition and the resultant paternity gains. We built a theoretical model to analyze such coevolutionary feedbacks between nuptial gift size (male trait) and propensity for multiple mating (female trait). Our genetically explicit, individual-based computer simulations demonstrate that a positive correlation between donated gift size and the resultant paternity gain is a requisite for the co-occurrence of large-sized gifts and females competitive multiple mating for the gifts. When donation of gifts imposes monandry, exaggeration in nuptial gift size also occurs under the assumption that the last male monopolizes paternity. We also analyzed the causes and consequences of the evolution of a female persistence trait in trading of nuptial gifts, that is, double receptacles for nuptial gifts known to occur in an insect group with a "female penis" (Neotrogla spp.).

evolutionary biology↗

bioRxiv2020

Cooperative interactions among females can lead to even more extraordinary sex ratios

Hamiltons local mate competition theory provided an explanation for extraordinary female biased sex ratios in a range of organisms. When mating takes place locally, in structured populations, a female biased sex ratio is favoured to reduce competition between related males, and to provide more mates for males. However, there are a number of wasp species where the sex ratios appear to more female biased than predicted by Hamiltons theory. We investigated theoretically the extent to which cooperative interactions between related females can interact with local mate competition to favour even more female biased sex ratios. We found that: (i) cooperative interactions between females can lead to sex ratios that are more female biased than predicted by local competition theory alone; (ii) sex ratios can be more female biased when the cooperative interactions are offspring helping parents before dispersal, rather than cooperation between siblings after dispersal. Our results can be applied to a range of organisms, and provide an explanation for the extreme sex ratio biases that have been observed in Sclerodermus and Melittobia wasps.

ecology↗

bioRxiv2020

Persistence of a Wolbachia-driven sex ratio bias in an island population of Eurema butterflies

It is generally believed that when maternally inherited sex ratio distorters become predominant, either the host population goes extinct or nuclear suppressors evolve in the host. Here, we show an empirical case where all-female-producing Wolbachia is likely to be stably maintained at a high frequency. On an island population of the butterfly Eurema mandarina, a Wolbachia strain wFem, which makes female hosts produce all-female offspring without sibling lethality (female drive), is highly prevalent. We found that, with some fluctuations, wFem appeared to be stably maintained for at least 12 years at a high frequency, resulting in the existence of an abnormally high number of virgin females. Interestingly, comparison between sex ratios of captive individuals and sex ratios deduced from wFem frequencies suggested a plastic behavioral change of males and females in response to the shift of sex ratios. wFem presence does not affect brood size but has a slightly negative effect on body size. Stable coexistence of wFem-positive and -negative females in the population may be explained via mate choice by males, which keeps wFem in check. Taken together, this butterfly population is an attractive model for future studies on the population dynamics of sex ratios and mating behavior.

evolutionary biology↗

bioRxiv2018

Occurrence of diamondback moths Plutella xylostella and their parasitoid wasps Cotesia vestalis in mizuna greenhouses and their surrounding areas

We observed the seasonal occurrence of diamondback moth (DBM) larvae, Plutella xylostella (Lepidoptera: Plutellidae), and their native parasitoid wasps, Cotesia vestalis (Hymenoptera: Braconidae), on mizuna plants, Brassica rapa var. laciniifolia (Brassicales: Brassicaceae), in three commercial greenhouses and on wild cruciferous weeds, Rorippa indica (Brassicales: Brassicaceae), in the surrounding area in the Miyama countryside in Kyoto, Japan. The occurrences of DBM larvae in greenhouses followed their occurrence in the surrounding area: however, some occurrences of DBM in greenhouses took place when the DBM population in the surrounding was rather low. This suggests that the occurrence of DBM in greenhouses cannot always be explained by its seasonal occurrence in the surrounding areas. The occurrence of C. vestalis followed that of DBM larvae in mizuna greenhouses and in the surrounding areas. No C. vestalis were recorded in greenhouses when DBM was not present. Cotesia vestalis females preferred volatiles emitted from DBM-infested mizuna plants to those from uninfested conspecifics under laboratory conditions. Natural HIPVs (herbivory-induced plant volatiles) emitted from DBM-infested mizuna plants in greenhouses probably attracted C. vestalis from the surrounding area to cause their co-occurrence.

ecology↗