Biology subjects

Mlejnek, J.

Publications and source records attributed to Mlejnek, J..

4 recordsLinked to original sources

bioRxiv2026

A Lineage-Specific Peptide Suppresses Juvenile Hormone to Drive Reproductive and Longevity Reprogramming in Ants

In ants and other eusocial insects, reproductive division of labor is tightly regulated by juvenile hormone (JH), which suppresses reproduction in most individuals to maintain the worker caste. However, how social cues trigger systemic JH suppression to permit reproductive activation remains unclear. In the ant Harpegnathos saltator, workers respond to queen loss by engaging in sustained ritualistic dueling and transitioning into reproductive, long-lived pseudoqueens (gamergates). This provides a powerful model for investigating the molecular basis of socially induced plasticity. We examined the hemolymph proteome of transitioning ants and identified HCRG1, a lineage-restricted peptide upregulated during dueling, as a circulating factor that physically interacts with Hex70c, a broadly conserved JH-binding Hexamerin. HCRG1 promotes ovarian development by antagonizing JH signaling. Expression of ant HCRG1 in the heterologous solitary model Drosophila also extends lifespan. These findings identify an evolutionarily derived circulating factor that links social sensory perception to systemic JH suppression, enabling coordinated reproductive and longevity transitions in a social insect.

evolutionary biology↗

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↗

bioRxiv2017

Olfactory Receptors Are Required For Social Behavior And Neural Plasticity In Ants, As Evidenced By CRISPR-Mediated Gene Knockout

The chemosensory system is key to establishing and maintaining social structure in eusocial insects. Ants exhibit cooperative colonial behaviors reflective of an advanced form of sociality with an extensive dependency on communication. Cuticular hydrocarbons (CHCs) serve as pheromones and cues that regulate multiple aspects of social interactions and behaviors in ants. The perception of CHCs entails odorant receptor neurons (ORNs) that express specific odorant receptors (ORs) encoded by a dramatically expanded Or gene family in ants. Until recently, studies of the biological functions of ORs in eusocial insects were stymied by the lack of genetic tools. In most eusocial insect species, only one or a few queens in a colony can transmit the genetic information to their progeny. In contrast, any worker in the ant Harpegnathos saltator can be converted into a gamergate (pseudo-queen), and used as a foundress to engender an entire new colony and be crossed for genetic experiments. This feature facilitated CRISPR-Cas9 gene targeting to generate a germline mutation in the orco gene that encodes the obligate co-receptor whose mutation should significantly impact ant olfaction. Our results show that Orco exhibits a conserved role in the perception of general odorants but also a role in reproductive physiology and social behavior plasticity in ants. Surprisingly, and in contrast to other insect systems, the loss of OR functionality also dramatically reduces the development of the ant antennal lobe where ORNs project. Taken together, these findings open the possibility of studying the genetics of eusociality and provide inroads towards understanding the function of the expanded ORs family in eusocial insects in regulating caste determination, social communication and neuronal plasticity.

neuroscience↗