Question

Based on your understanding of sea urchin and fruit fly gastrulation, would you expect the ventral furrowing of the fruit fly to require an epithelial-to-mesenchymal transition? Why or why not?

Please answer it in your own words.

Answer 1

Yes, the ventral furrowing requires epithelial to mesenchymal transition.

This is because :

• Gastrulation movements in Drosophila segregate the mesoderm, endoderm, and ectoderm.

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• The mesoderm (about 1000 cells) constituting the ventral midline of the embryo—folds inward to produce the ventral furrow.

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• The furrow formed pinches off from the surface to become a ventral tube within the embryo which then flattens to form a layer of mesodermal tissue beneath the ventral ectoderm.

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• The endoderm invaginates as two small pocket like structure at the anterior and posterior ends of the ventral furrow and the pole cells are internalized along with the endoderm.

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• At this time, the embryo bends to form the cephalic furrow.

Thus the epithelial to mesenchymal transition helps in the ventral furrowing of the fruitfly while gastrulation.

Also, the ectodermal cells on the surface and the mesoderm undergo convergence and extension, migrating towards the ventral midline to form the germ band, which wraps around the dorsal surface of the embryo and later on helps in the formation of body segments.