Biology subjects

Oliver, K. M.

Publications and source records attributed to Oliver, K. M..

4 recordsLinked to original sources

bioRxiv2025

Phenotypic divergence is driven by mobile genetic elements in a heritable insect symbiont

AO_SCPLOWBSTRACTC_SCPLOWHeritable microbes profoundly influence insect biology, yet the traits they confer often evolve rapidly and differ among closely related symbiont strains. Despite their importance, we lack a clear understanding of how novel traits arise in symbiosis and how this diversity influences host ecology in natural populations. The aphid facultative symbiont Regiella insecticola is ideally suited to this question because of its strong lineage-specific variation in host benefits. By generating 20 high-quality genomes, we found that Regiellas evolution is driven largely by gene gains mediated by mobile genetic elements. We identified a plasmid (pRILSR1) that encodes a type IV secretion system and a highly expressed predicted effector that has been convergently acquired by Regiella strains from pea aphids. Notably, only pRILSR1-bearing strains confer protection against the specialist fungal pathogen Pandora neoaphidis, indicating that gains and losses of the plasmid underlie the evolution of this key defensive phenotype. Using a multi-year field study, we further show that the pRILSR1 plasmid is strongly associated with Regiella found in pea aphid populations adapted to specific host plants, driving variation in symbiont-mediated defense across populations. Together, our results show that mobile genetic elements generate key adaptive traits in microbial symbionts and, in doing so, drive phenotypic divergence among host populations.

evolutionary biology↗

bioRxiv2025

Phage toxin variants are linked to protection specificity in a defensive symbiont

Insects often depend on symbiotic bacteria for protection, yet the mechanisms by which these microbes target specific natural enemies remain poorly understood. In aphids, different strains of the facultative symbiont Hamiltonella defensa provide highly specific protection against particular species of parasitoid wasps. To uncover the genetic basis of this specificity, we analyzed 26 Hamiltonella genomes and their toxin-encoding APSE bacteriophages with distinct protective phenotypes. Our analyses revealed that Hamiltonella strains share a conserved core genome but differ significantly in accessory gene content, reflecting their distinct evolutionary origins. Strikingly, we show that variation in toxin types is the key distinguishing feature of APSE phages in Hamiltonella strains that protect against different parasitoid species. These toxin repertoires include several novel candidates, such as variants with MAC/perforin domains and leucine-rich repeat (LRR) proteins previously unreported in insect defensive symbionts. We also reveal cases of multiple co-integrated APSE phages carrying different toxins within a single genomic locus. These findings implicate phage-borne toxins as primary determinants of enemy-specific defense and point to phage-driven toxin diversification as a major force shaping the functional evolution of this symbiosis. This work highlights how mobile genetic elements influence the ecological roles and diversification of protective symbionts.

evolutionary biology↗

bioRxiv2025

Derivation and analysis of human somatic sensory neuron subtypes facilitated through fluorescent hPSC reporters

Peripheral sensory neuropathy (PSN) is associated with several devastating neurological conditions, yet effective strategies to prevent or alleviate the consequences of PSN are nearly non-existent. A major challenge in the development of better therapeutic interventions is the lack of appropriate human model systems. Human induced pluripotent stem cell (hiPSC)-derived somatosensory neurons present a promising strategy to overcome this issue but remain of limited translational utility, in part due to the low efficiency and lack of sensory subtype selectivity of the existing sensory neuron derivation protocols. To improve upon iPSC-based somatosensory disease models, we here describe the generation and validation of a genetic toolset to fluorescently label all or distinct (nociceptor, low threshold mechanoreceptor, and proprioceptor) somatosensory subtypes. These new resources will be transformative for hPSC-based approaches in PSN disease modeling - a critical step towards translating new findings into clinically relevant therapeutic strategies.

neuroscience↗

bioRxiv2020

Molecular development of muscle spindle and Golgi tendon organ sensory afferents revealed by single proprioceptor transcriptome analysis

Anatomical and physiological analyses have long revealed differences between proprioceptive groups Ia, II, and Ib sensory neurons, yet the molecular correlates of these three muscle afferent subtypes remain unknown. We performed single cell RNA sequencing of genetically identified adult proprioceptors and, using unbiased bioinformatics approaches, detected five molecularly distinct neuronal clusters. Validation of cluster-specific transcripts in dorsal root ganglia (DRG) and skeletal muscle provides evidence these clusters correspond to functionally distinct muscle spindle (MS) or Golgi tendon organ (GTO) afferent proprioceptors. Remarkably, while we uncovered just one type of GTO afferents, four of the five clusters represent MS afferents, thus demonstrating a previously unappreciated diversity among these muscle proprioceptors. In vitro electrophysiological recordings reveal just two broadly distinct proprioceptor types, and suggest that the refinement of functional subtype diversity may occur along multiple axes of maturation. Lineage analysis between proprioceptor transcriptomes at different developmental stages show little or no correlation for transcripts that define adult MS or GTO afferents, supporting the idea that proprioceptor subtype identity emerges late in development. Together, our data provide the first comprehensive molecular signature for groups Ia and II MS afferents and group Ib GTO afferents, and offer new strategies for genetic interrogation of the role of these individual proprioceptor subtypes in regulating voluntary motor behavior.

neuroscience↗