The chorion genes of the medfly. II. DNA sequence evolution of the autosomal chorion genes s18, s15, s19 and s16 in Diptera

We present a total of approximately 15 kb of DNA sequences, encompassing fo ur chorion genes: Ccs18. Ccs15, Ccs19, Ccs16 and their flanking DNA in the medfly C. capitata. Comparison of coding regions, introns and intergenic se quences in five Dipteran species. D. melanogaster. D. subobscura, D. virili s. D. grimshawi and C. capitata documented an extensive divergence in intro ns and coding regions, but few well conserved elements in the proximal 5 ' flanking regions in all species. These elements are related to conserved re gulatory features of three of the gents, including tissue- and temporal reg ulation. In the fourth, gene s15, significant alterations in the 5 ' flanki ng region may be responsible for its changed temporal regulation in C. capi tata. One long intergenic sequence. located in the distal 5 ' Ranking regio n of gene s18. is homologous to ACE3. a major amplification central element and contains an 80-bp AT-rich sequence, known to stimulate strong binding of the origin recognition complex (ORC) in D. melanogaster. Analysis of the nucleotide composition of all chorion genes in C. capitata and D.,melanoga ster showed that C, capitata exhibit less biased representation of synonymo us codons than does D. melanogaster. (C) 2001 published by Elsevier Science B.V. All rights reserved.