The applications of studying the early development of insects range from agriculture to material science. In agriculture creating new kinds of pesticides and in material science making new... Show moreThe applications of studying the early development of insects range from agriculture to material science. In agriculture creating new kinds of pesticides and in material science making new materials that avoid desiccation. After Drosophila melanogaster, Tribolium castaneum is becoming the most used insect in developmental biology because Tribolium’s development is more representative to the rest of the insects’ development than Drosophila’s. In this thesis the early development of Tribolium is studied, specifically cellularization and serosal window closure. Cellularization is the formation of the cells. We discovered that the mechanical interaction between cells leads to the formation of a Voronoi tilling in the cells’ arrangement. Furthermore, we studied the genetics of cellularization by silencing genes related to junction proteins. We found that Innexin 7 protein is central to finish the process of cellularization. Serosal window closure is the first cell rearrangement to create a cover for the embryo. We looked for proteins involved in serosal window closure. We found that protein Laminin α1,2, β and γ is a key cell component in the process of serosal window closure. In conclusion, during development there are physical and genetics factors acting at the same time. Show less
Zee, M. van der; Benton, M.A.; Vazquez Faci, T.; Lamers, G.E.M.; Jacobs, C.G.C.; Rabouille, C. 2015
In insects, the fertilized egg undergoes a series of rapid nuclear divisions before the syncytial blastoderm starts to cellularize. Cellularization has been extensively studied in Drosophilamelanog...Show moreIn insects, the fertilized egg undergoes a series of rapid nuclear divisions before the syncytial blastoderm starts to cellularize. Cellularization has been extensively studied in Drosophilamelanogaster, but its thick columnar blastoderm is unusual among insects. We therefore set out to describe cellularization in the beetle Tribolium castaneum, the embryos of which exhibit a thin blastoderm of cuboidal cells, like most insects. Using immunohistochemistry, live imaging and transmission electron microscopy, we describe several striking differences to cellularization in Drosophila, including the formation of junctions between the forming basal membrane and the yolk plasmalemma. To identify the nature of this novel junction, we used the parental RNAi technique for a small-scale screen of junction proteins. We find that maternal knockdown of Triboliuminnexin7a (Tc-inx7a), an ortholog of the Drosophila gap junction gene Innexin 7, leads to failure of cellularization. In Inx7a-depleted eggs, the invaginated plasma membrane retracts when basal cell closure normally begins. Furthermore, transiently expressed tagged Inx7a localizes to the nascent basal membrane of the forming cells in wild-type eggs. We propose that Inx7a forms the newly identified junctions that stabilize the forming basal membrane and enable basal cell closure. We put forward Tribolium as a model for studying a more ancestral mode of cellularization in insects. Show less
