Project 20.3

My research project explores the relationship between sexual dimorphism and development in termites. In early development, I investigate the onset and mechanisms of dosage compensation and sex determination. Furthermore, I will study what happens during caste changes and assess the interaction between sex and caste, using molecular markers, RNAi, and differential gene expression analysis.

My research project investigates the complex relationship between sex-biased gene expression and caste differentiation during development in termites. Termites are eusocial hemimetabolous insects with an XY sex determination system. In their society there are different castes which differ in morphology: workers, soldiers and reproductives. Lower termite species exhibit an exceptional developmental plasticity, and individuals can change caste throughout their life depending on many social and environmental factors. Male and female individuals are present in every caste, but workers and soldiers cannot reproduce; with soldiers being completely sterile while workers still retain the potential to develop into reproductives.

My study focuses on Reticulitermes grassei and Reticulitermes flavipes where caste change is tied to reproductive maturity. My project investigates the connection between caste and sexual dimorphism, and what happens genetically if the completely sterile caste pathway is chosen. I will explore whether sex-biased gene expression increases progressively through termite development. Thus, I aim to identify when sex determination and dosage compensation begin, and which molecular mechanisms are involved. In fact, prior studies showed full dosage compensation is achieved in reproductives of these species, but the onset mechanism is still unclear.

The research involves analyzing gene expression changes across various developmental stages and castes. Sex-specific gene markers and isoforms will be identified to develop a molecular sexing technique. RNA interference (RNAi) will help to test the role of specific sex-related genes throughout termite development. These methods will allow me to verify how gene function correlates with observed morphological and reproductive traits.

By the study of the crosstalk between sex and caste determination, the project seeks to discover how sexual dimorphism is regulated in this high developmental flexibility system.

Does sex-biased expression increase linearly with development? What happens to sexual traits when an individual follows a developmental pathway to the soldier caste? Which are the key regulatory genes driving these transitions?

The results of this study could offer new insights to the evolution of sex determination systems and gene expression regulation differences between the sexes in these social insects. Understanding these mechanisms could support research in other eusocial organisms and expand knowledge on how gene regulation in complex social structures works.