Wnt and Fgf signaling pharmacological inhibition affect posterior growth during Tribolium castaneum germband elongation

Axial elongation and sequential segmentation are developmental processes that occur simultaneously and are highly conserved in vertebrates and most arthropods. These features rely on the dynamic expression of a genetic network that establishes the segmented patterning and regulates various cellular behaviors, including tissue rearrangements and cell divisions. In vertebrates, Wnt and Fgf signaling are essential for these processes. While some studies in arthropods have linked these pathways to segmentation, there is still much to discuss regarding their regulatory role in cellular processes. In this study, we pharmacologically inhibited Wnt and Fgf signaling pathways by exposing developing Tribolium castaneum embryos to IWP-3 and SU5402, respectively. We observed that both treatments resulted in a shortening of the embryos and a decrease in the number of cell divisions during a period characterized by high proliferation rates. Although the segmented patterning was not disrupted, the segments were smaller in the embryos treated with the Fgf inhibitor than in the controls. Additionally, time-lapse imaging revealed that cell movement along the anteroposterior axis was affected in the IWP-3-treated embryos. In contrast, Fgf inhibition primarily altered the direction of cell movements at the posterior end of the embryo. Our findings provide insight into the roles of Wnt and Fgf signaling pathways in regulating significant cellular behaviors during the posterior growth of Tribolium and possibly other arthropods.