Concerted Evolution of the Replication-Dependent Histone Gene Family in Drosophila immigrans

Abstract

The replication-dependent histone genes in Drosophila immigrans were analyzed for elucidating the evolutionary mechanism of the histone multigene family. A region of approximately 3.9 kb containing H2A-H2B-H1 genes was cloned. Six independent clones were sequenced and analyzed for nucleotide variability. The average nucleotide sequence identity in the region among repetitive copies was more than 99%, indicating that the histone multigene family in D. immigrans has evolved in a concerted fashion and with a similar level as in D. melanogaster. Amino acid variants were found at a low frequency. Analysis of the GC content at the 3rd codon position of histone genes revealed that a change in GC content, i.e., a decrease, observed in D. hydei and D. americana has occurred after the divergence of an ancestor of these two species from D. immigrans.