Transcription factor function in hormonally controlled processes: the role of a neurally expressed POU protein in insect female fertility

• Applicant: Dr. Vera Terblanche
• Subject Area: Evolutionary Cell and Developmental Biology (Zoology) ; General Genetics and Functional Genome Biology ; Developmental Biology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 575582783

Insect fertility is pivotal for species success and the evolution of divergent reproductive strategies allows for ecological adaptability. Females are confronted with a trade-off between nutrient intense egg production and their own viability. The correct egg size for providing sufficient nutrients to the offspring needs to be maintained and the number of eggs needs to be limited. Different aspects of female fertility, such as oogenesis, egg laying behaviour and mating capacity are under the influence of genetic factors. The insect hormonal systems juvenile hormone, ecdysone and neuropeptides coordinate female egg production and genetic regulators influencing female fertility may often interact with these pathways. However, few transcriptions factors that regulate hormonal pathway or other aspects of fertility have been identified in insects other than the fly Drosophila melanogaster, and, apart from insulated insights, it is not known in how far the genetic factors identified in the fly have conserved functions in other insects. We have newly found that in the beetle Tribolium castaneum the so far little-studied POU transcription factor pdm3, which is expressed in the central nervous system, specifically functions in the limitation of female fertility as an RNAi knock down increases egg number. Interestingly, we found that some genes involved in ecdysone and juvenile hormone metabolism and different cytochrome P450 enzymes with yet unknown functions, as well as insulin like peptide, are repressed by pdm3, in addition to some more factors that may act on other aspects of fertility. This indicates that pdm3 is a neural regulator of fertility and its action possibly includes balancing different hormonal systems required for normal egg production. Intrigued by these preliminary finding I am planning to elaborate on the function of pdm3 in T. castaneum and in the fly D. melanogaster (through a collaboration) in a comparative functional genetics and genomics approach. Using newly established CRISPR-Cas9 methods in the beetle we are going to create and analyse mutant- and reporter lines for pdm3, and a line that will be used for CUT & RUN based genome-wide target analysis. This approach will be mirrored in D. melanogaster by my collaborator, creating two datasets that will allow for a rarely performed cross-species evolutionary comparison of transcription factor binding profiles. The biological processes through which pdm3 acts on target genes will be revealed, and how its function may have diverged between different insect species in accordance with biological differences in egg production. Localising expression of pdm3 in the nervous system and neuroendocrine glands will then open the opportunity to investigate functions of specific cells in the control of fertility and potentially identify novel circuits involved in the control of insect fertility.

• DFG Programme: Research Grants