Meeting Abstract

P1.80  Monday, Jan. 4  Evolutionary Analysis of Single Nucleotide Insertions in the Mitochondrial Genomes of Glass Sponges HOPKINS, JM*; HAEN, KM; LAVROV, DV; Iowa State University jenah@iastate.edu

Occasionally, mitochondrial (mt) coding sequences can contain extra nucleotides. In general, the presence of extra nucleotides in coding sequences may be indicative of nuclear transfer of mitochondrial genes (numts) or RNA editing. Recently, a growing number of these cases appear to be due to translational frameshifting. The phenomenon known as +1 translational frameshifting is a mechanism by which an extra nucleotide in a protein coding sequence is left untranslated through a process of ribosomal bypass. Often this mechanism entails the use of a rare codon in the original reading frame which acts as a frameshifting signal. Single base insertions have been reported in the mtDNA of the eastern oyster, as well as for several species of ants, birds, and turtles. We had previously noted incidences of single nucleotide insertions in the mitochondrial protein coding genes of two glass sponges (Phylum Porifera, Class Hexactinellida). More recently, we expanded the breadth of our taxon sampling to include members of two orders and six families of the Hexactinellida. Base insertions in hexactinellid mt protein coding genes appear to conform to the +1 frameshifting pattern due to a high degree of sequence conservation and a distinct pattern of codon usage. Here we describe putative translational frameshifting in the nad2, cox3, and cox1 protein coding genes of Hertwigia falcifera, Sympagella nux, Iphiteon panicea, Euretidae sp, and two species of Aphrocallistidae, and we place these results in an evolutionary context.