Microcloning and characterization of the early ecdysone puff region 2B of the X chromosome of Drosophila melanogaster

Abstract

Chromosomal region 2B from Drosophila polytene chromosomes has been microdissected and the DNA extracted and cloned in a lambda vector. Many of the clones have been cytologically and cytogenetically mapped with the aid of chromosome rearrangements. Some of the clones have been mapped to band 2B5, from which an early ecdysone puff develops. One of the clones was further characterized (λ 147) and was found to be complementary to several RNA transcripts. The production of at least one of the transcripts is stimulated in vitro by 20-OH-ecdysone, and its increase parallels increases in ecdysteroid titre found in late embryos and early third instar larvae but does not coincide with increases in pupal hormone. Although 2B5-deficient mutants are able to develop until pupariation, the RNA complementary to the cloned sequence is already present in embryos. We present evidence that this embryonic RNA is maternally inherited.