Genetic,cytological, and ultrastructural characterization of a temperature-sensitive lethal in Drosophila melanogaster

Genetic analysis of a strain of Drosophila melanogaster revealed that a recessive mutation [l(1)ER^ts] causing temperature-sensitive embryonic lethality is located in the distal region of the X chromosome approximately at map position 18. At 22–25°C mutant embryos exhibit normal viability, and all eggs arrest prior to gastrulation if they are reared at 29°C. The mutant is biphasic, exhibiting a maternal effect which is expressed throughout the first 8 hr of development as well as a second temperature-sensitive period (TSP) during the first 3 days of larval life. Larvae exposed to the restrictive temperature (RT) during the second TSP must also spend the remainder of larval and pupal life and the time of normal eclosion at RT to die as fully developed pupae which fail to eclose. Light and electron microscopy of arrested embryos reveal disturbances in the distribution of nuclei, cytoplasm, and yolk and abnormal configurations of rough endoplasmic reticulum. The cause of pupal death during the second lethal period is unknown.