BMP signaling in camponotus floridanus and its alteration in the presence of obligate endosymbionts

Gene Regulatory Networks (GRNs) composed of interacting genes are responsible for pattern formation in a wide variety of developmental contexts. All bilaterally symmetric animals face the problem of setting up their axis of symmetry through developmental patterning during embryogenesis. GRNs underlie these developmental patterning and morphogenetic processes, and changes in the interactions cause changes in phenotype. One of the most thoroughly characterized GRN is the dorsoventral (DV) patterning system, driven by Bone Morphogenetic Protein (BMP) signaling pathway in many insects. Although the establishment of the DV axis is well studied in Drosophila melanogaster, it is largely unknown in the case of ants. Moreover, in the case of insects that host cellular endosymbionts, additional challenges are faced because of the interactions between the endosymbiont and intercellular signals of the host developmental gene regulatory networks. In this thesis, the effect of the presence of endosymbiont on the formation of the DV axis of the host was investigated. In order to understand how the establishment of the DV axis can be altered in case of the presence of the endosymbiont, these processes were characterized in carpenter ant Camponotus floridanus. BMP signaling, which primarily controls DV patterning in animals, was characterized. Molecular techniques such as gene cloning, in situ hybridization, and RNA interference were used to examine the expression and function of developmental genes that are particularly involved in DV axis formation. Our results revealed that BMP signaling was active during early development of C.floridanus. Gene expression studies showed that ligands decapentaplegic (dpp), glass-bottom boat (gbb); metalloprotease tolloid (tld); antagonists twisted gastrulation (tsg), short gastrulation (sog); type I receptor thickveins (tkv) and type II receptor punt were expressed in the embryo and germline capsule while they were not expressed in the extraembryonic serosa or amnion excluding dpp, sog. dpp and sog were expressed in the amnion while sog was expressed in the serosa. dpp, gbb and tkv were expressed in the bacterial region at early stages as well as tld, sog and tkv were expressed in the bacteriocyte region in the egg at later stages. Gene function studies revealed that the reduction or loss of BMP signalling affects the identity of the three embryonic germlayers – ectoderm, mesoderm, and endoderm. In addition, the formation of the extraembryonic serosa was affected by the reduction of BMP signalling, whereas the identity of the amnion may be independent of this pathway.