The Interactive Fly
Genes involved in tissue and organ development
The tracheaee constitute the respiratory system of the fly. Made up of tubules that ramify throughout the body, trachea terminate in enlargements called air sacs, through which gas exchange takes place. Spiracles are the external tracheal apertures, repeated segmentally on either side of the thorax and abdomen.
The embryonic tracheal system is an epithelial tubular network established from defined sets of ectodermal precursor cells. At stage 10 of embryonic development, lateral ectodermal clusters of cells on both sides of the 10 posterior (thoracic 2 and 3 and abdominal 1 through 8) parasegments assume a tracheal placode fate [Images]. These cells, about 80 in each placode invaginate at stage 11 to form tracheal pits. The subsequent formation of the tracheal tree occurs without further cell division. First the cells migrate in a distinct pattern, then they fuse with other tracheal cells from adjacent segments to form a continuous tubular network. Terminal tracheal cells send long extentions toward the target cells. (Wilk, 1996).
Wilk, R., Weizman, I. and Shilo, B-Z. (1996). trachealess encodes a bHLH-PAS protein that is an inducer of tracheal cell fates in Drosophila. Genes and Devel. 10: 93-102
Genes involved in organ development
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