Evolution of the Drosophila broad locus: the Manduca sexta broad Z4 isoform has biological activity in Drosophila
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The Drosophila melanogaster broad locus is essential for normal metamorphic development. Broad encodes three genetically distinct functions (rbp, br, and 2Bc) and a family of four zinc-finger DNA-binding proteins (Z1-Z4). The Z1, Z2, and Z3 protein isoforms are primarily associated with the rbp, br, and 2Bc genetic functions respectively. The Z4 protein isoform also provides some rbp genetic function, however an essential function for the Z4 isoform in metamorphosis has not been identified. To determine the degree of conservation of Z4 function between the tobacco hornworm Manduca sexta and Drosophila we generated transgenic Drosophila expressing the Manduca broad Z4 isoform and used this transgene to rescue rbp mutant lethality during Drosophila metamorphosis. We find that the Manduca Z4 protein has significant biological activity in Drosophila with respect to rescue of rbp-associated lethality. There was also some overlap in effects on cuticle gene expression between the Manduca Z4 and Drosophila Z1 isoforms that was not shared with the Drosophila Z4 isoform. Our findings show that Z4 function has been conserved over the 260-million-year period since the divergence of Diptera and Lepidoptera, and are consistent with the hypothesis that the Drosophila Z4 and Manduca Z4 isoforms have essential roles in metamorphosis.
KeywordsBR-C Broad-Complex Ecdysone Metamorphosis Gene duplication
- Bayer CA., von Kalm L, Fristrom JW (1996a) Gene regulation in imaginal disc and salivary gland development during Drosophila metamorphosis. In: Gilbert LI, Atkinson BG, Tata JR (eds) Metamorphosis: post-embryonic reprogramming of gene expression in amphibian and insect cells. Academic Press, New York, pp 321–361Google Scholar
- Kukalova-Peck J (1991) Fossil history and the evolution of hexapod structures. In: Naumann ID, Carne PB, Lawrence JF, Nielsen ES, Spradbery JP, Taylor RW, Whitten MJ, Littlejohn MJ (eds) The insects of Australia, vol 1. Cornell University Press, Ithaca, N.Y., pp 141–179Google Scholar
- Restifo LL, White K (1992) Mutations in a steroid hormone-regulated gene disrupt the metamorphosis of internal tissues in Drosophila: salivary glands, muscle, and gut. Roux's Arch Dev Biol 201:221–234Google Scholar
- Thummel CS, Pirrotta V (1992) New pCaSpeR P element vectors. Dros Inf Serv 71:150Google Scholar