Length variation and secondary structure of introns in the Mlc1 gene in six species of Drosophila.
A nearly universal feature of intron sequences is that even closely related species exhibit a large number of insertion/deletion differences. The goal of the analysis described here is to test whether the observed pattern of insertion/deletion events in the genealogy of the myosin alkali light chain (Mlc1) gene is consistent with neutrality, and if not, to determine the underlying forces of evolutionary change. Mlc1 pre-mRNA is alternatively spliced, and one constraint is that signals necessary for tissue-specificity of directed splicing must be conserved. If the total length of an intron is functionally constrained, then the distribution of indels on branches of the gene genealogy should reflect a departure from randomness. Here we perform a phylogenetic analysis, inferring ancestral states wherever possible on a phylogeny of 29 alleles of Mlc1 from six species of Drosophila. Observed patterns of indels on the genealogy were compared to those from simulated data, with the result that we cannot reject the null hypothesis of neutrality. A clear departure from a neutral prediction was seen in the excess folding free energy predicted for the introns flanking the alternatively spliced exon. Relative rate tests also suggest a retardation in the rate of Mlc1 sequence evolution in the simulans clade.
Clark
A G
AG
Department of Biology, Institute of Molecular Evolutionary Genetics, Pennsylvania State University, University Park 16802, USA. c92@psuvm.psu.edu
Leicht
B G
BG
Muse
S V
SV
D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000302:isolation & purification; D004251:DNA Transposable Elements; D004330:Drosophila / Q000145:classification / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics; D017344:Genes, Insect; D007438:Introns; D008969:Molecular Sequence Data; D018994:Myosin Light Chains / Q000235:genetics*; D010802:Phylogeny; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D004251:DNA Transposable Elements; D018994:Myosin Light Chains; D004247:DNA