Biology subjects

Sieriebriennikov, B.

Publications and source records attributed to Sieriebriennikov, B..

7 recordsLinked to original sources

bioRxiv2025

Sensitivity to Cuticular Hydrocarbons Across the Odorant Receptor Family in the Indian Jumping Ant

Eusocial insects rely on the olfactory detection of cuticular hydrocarbons (CHCs) to mediate fundamental eusocial behaviors, such as nestmate recognition, and reproductive division of labor. In the ponerine ant Harpegnathos saltator, highly expanded odorant receptor (OR) families detect CHCs and mediate these eusocial behaviors at the molecular level. Previous studies have characterized H. saltator OR (HsOr) genes within the 9-exon and other large subfamilies, but it remains unclear how other HsOr subfamilies may contribute to CHC detection. Using heterologous expression in Drosophila melanogaster olfactory neurons, we characterized HsOr sensitivity more broadly across the gene family, outside the 9-exon subfamily, to a panel of hydrocarbons (HC). Twenty-three HsOrs across sixteen subfamilies were screened, and several were found to be broadly tuned and weakly responsive to the HCs tested, except for HsOr152 which showed narrow tuning to a single HC found on the H. saltator cuticle. Lastly, we compiled and analyzed the HC responses from the 70 HsOrs from this and previous studies. This analysis suggests a combinatorial coding model of CHC detection, where several receptors across different subfamilies can contribute to the detection and discrimination of different CHCs. Our characterization of HsOrs provides functional insights into the molecular mechanisms of chemical communication among eusocial insects.

molecular biology↗

bioRxiv2024

Spatial constraints and cell surface molecule depletion structure a randomly connected learning circuit

The brain can represent almost limitless objects to "categorize an unlabeled world" (Edelman, 1989). This feat is supported by expansion layer circuit architectures, in which neurons carrying information about discrete sensory channels make combinatorial connections onto much larger postsynaptic populations. Combinatorial connections in expansion layers are modeled as randomized sets. The extent to which randomized wiring exists in vivo is debated, and how combinatorial connectivity patterns are generated during development is not understood. Non- deterministic wiring algorithms could program such connectivity using minimal genomic information. Here, we investigate anatomic and transcriptional patterns and perturb partner availability to ask how Kenyon cells, the expansion layer neurons of the insect mushroom body, obtain combinatorial input from olfactory projection neurons. Olfactory projection neurons form their presynaptic outputs in an orderly, predictable, and biased fashion. We find that Kenyon cells accept spatially co-located but molecularly heterogeneous inputs from this orderly map, and ask how Kenyon cell surface molecule expression impacts partner choice. Cell surface immunoglobulins are broadly depleted in Kenyon cells, and we propose that this allows them to form connections with molecularly heterogeneous partners. This model can explain how developmentally identical neurons acquire diverse wiring identities.

neuroscience↗

bioRxiv2023

Activity-dependent survival of odorant receptor neurons in ants

Olfaction is essential for complex social behavior in eusocial insects. To discriminate complex social cues, ants evolved an expanded number of odorant receptor (Or) genes. Unlike most insect species, mutations in the obligate odorant co-receptor gene orco lead to loss of [~]80% antennal lobe glomeruli in ants. However, its cellular mechanism remains unclear. Here we demonstrate that this surprising neuronal phenotype results from massive apoptosis of odorant receptor neurons (ORNs) in the mid- to late-stages of pupal development. Further bulk and single-nucleus transcriptome analysis show that, although the majority of orco-expressing ORNs die in orco mutants, a small proportion of them survive: they express ionotropic receptor (Ir) genes that form IR complexes. In addition, we found that some Or genes are expressed in mechanosensory neurons as well as non-neuronal cells, possibly due to the leaky regulation from nearby non-Or genes. Our findings suggest that chemosensory receptors are required for activity-dependent survival of developing ORNs in ants.

developmental biology↗

bioRxiv2022

Insulin signaling and extended longevity in ants

In most organisms, the cost of reproduction is a shorter lifespan. However, the reproductive caste in eusocial insect species (queen) exhibits an extraordinarily longer lifespan than non-reproductive castes (workers) despite having a similar genome, thus contradicting the aging dogma. In the absence of the queen, Harpegnathos saltator ants can undergo a caste switch from workers to reproductive pseudo-queens (gamergates). Gamergates exhibit a dramatically prolonged lifespan. When placed in the presence of a reproductive, they revert to worker status and their lifespan is then shortened accordingly. To understand this unique relationship between reproduction and longevity, we analyzed tissue-specific gene expression between castes. Insulin is upregulated in the gamergate brain that leads to oogenesis, but surprisingly correlates with extended longevity. This correlates with increased lipid synthesis and elevated production of vitellogenin in the fat body, which are both transported to the egg. We show that the production of vitellogenin in the fat body is due to the systemic activation of the MAPK branch of the insulin/IGF signaling (IIS)-pathway. In contrast, reduced expression of insulin receptors in the fat body of gamergates and the production in their developing ovary of an anti-insulin (Imp-L2) lead to the downregulation of the AKT/FOXO branch of the IIS-signaling pathway in the fat body, and to the dramatically extended longevity. This reveals a dual-pathway mechanism that reconciles increased longevity in the context of active reproduction in eusocial insects. One Sentence SummaryInsulin-dependent reproduction in ants correlates with extended longevity through insulin inhibition by anti-insulin Imp-L2.

physiology↗

bioRxiv2021

Genome annotation with long RNA reads reveals new patterns of gene expression in an ant brain

Functional genomic analyses rely on high-quality genome assemblies and annotations. Highly contiguous genome assemblies have become available for a variety of species, but accurate and complete annotation of gene models, inclusive of alternative splice isoforms and transcription start and termination sites remains difficult with traditional approaches. Here, we utilized full-length isoform sequencing (Iso-Seq), a long-read RNA sequencing technology, to obtain a comprehensive annotation of the transcriptome of the ant Harpegnathos saltator. The improved genome annotations include additional splice isoforms and extended 3 untranslated regions for more than 4,000 genes. Reanalysis of RNA-seq experiments using these annotations revealed several genes with caste-specific differential expression and tissue-or caste-specific splicing patterns that were missed in previous analyses. The extended 3 untranslated regions afforded great improvements in the analysis of existing single-cell RNA-seq data, resulting in the recovery of the transcriptomes of 18% more cells. The deeper single-cell transcriptomes obtained with these new annotations allowed us to identify additional markers for several cell types in the ant brain, as well as genes differentially expressed across castes in specific cell types. Our results demonstrate that Iso-Seq is an efficient and effective approach to improve genome annotations and maximize the amount of information that can be obtained from existing and future genomic datasets in Harpegnathos and other organisms.

genomics↗

bioRxiv2019

Conserved nuclear receptors controlling a novel trait target fast-evolving genes expressed in a single cell

Environment shapes development through a phenomenon called developmental plasticity. Deciphering its genetic basis has implications for understanding evolution and adaptation to novel environments, yet molecular studies are scarce. Here, we expanded the gene regulatory network controlling predatory vs. non-predatory morphology in the nematode Pristionchus pacificus. First, we isolated a mutant in the nuclear hormone receptor nhr-1 with a previously unseen phenotypic effect. It disrupts mouth-form determination and results in animals combining features of both wild-type morphs. Further, we identified common targets of NHR-1 and the previously identified nuclear hormone receptor NHR-40 through transcriptomics. Unlike their highly conserved regulators, the target genes have no orthologs in Caenorhabditis elegans and likely result from lineage-specific expansions. An array of transcriptional reporters revealed co-expression of all tested targets in the same pharyngeal gland cell. The morphological remodeling of this cell accompanied the evolution of teeth and predation, linking rapid gene turnover with morphological innovations.

developmental biology↗

bioRxiv2019

Evolution of neuronal anatomy and circuitry in two highly divergent nematode species

The nematodes C. elegans and P. pacificus populate diverse habitats and display distinct patterns of behavior. To understand how their nervous systems have diverged, we undertook a detailed examination of the neuroanatomy of the chemosensory system of P. pacificus. Using independent features such as cell body position, axon projections and lipophilic dye uptake, we have assigned homologies between the amphid neurons, their first-layer interneurons, and several internal receptor neurons of P. pacificus and C. elegans. We found that neuronal number and soma position are highly conserved. However, the morphological elaborations of several amphid cilia are different between them, most notably in the absence of winged cilia morphology in P. pacificus. We established a synaptic wiring diagram of amphid sensory neurons and amphid interneurons in P. pacificus and found striking patterns of conservation and divergence in connectivity relative to C. elegans, but very little changes in relative neighborhood of neuronal processes.\n\nImpact StatementThe substrate for evolutionary divergence does not lie in changes in neuronal cell number or targeting, but rather in sensory perception and synaptic partner choice within invariant, prepatterned neuronal processes.

neuroscience↗