European Journal of Protistology 48 (2012) 185–193 From cryptogene to gene? ND8 editing domain reduction in insect trypanosomatids Evgeny S. Gerasimov a , Alexei Yu. Kostygov b , Shi Yan a , Alexander A. Kolesnikov a,∗ a M.V. Lomonosov Moscow State University, Dept. Molecular Biology, 119991 Moscow, Russia b Zoological Institute RAS, 199034 St. Petersburg, Russia Received 13 July 2011; received in revised form 8 September 2011; accepted 9 September 2011 Available online 19 October 2011 Abstract Mitochondrial ND8 gene is pan-edited in most known trypanosomatid species and 5 ′ -edited only in a few trypanosomatid species. In this work, the ND8 nucleotide sequences from three species of insect trypanosomatids (“Wallaceina” sp. Wsd, Leptomonas rigidus and Leptomonas collosoma) were obtained and compared with previously known ND8 cryptogene sequences and mature mRNA sequences from other trypanosomatid species. We found a new pattern of editing: only 18 U residues are inserted in the 5 ′ region of the primary transcript in all investigated species and the potential start codon is encoded on the DNA level. This is the first case when a pre-edited ND8 sequence is found to contain a putative ORF. Previously, a 5 ′ -edited ND8 cryptogene was known only from Strigomonas oncopelti, but it contained only about half of the ORF and no start codon. Here we present the ND8 gene sequence from Angomonas deanei which has similar cryptogene structure. We also show that according to 18S rRNA phylogenetic analysis, the species with the encoded ORF group together and so do species with the 5 ′ -edited and pan-edited forms of the gene. This result sheds light on the evolution of cryptogene structure which involved multiple events of editing domain length reduction. © 2011 Elsevier GmbH. All rights reserved. Keywords: Trypanosomatids; Phylogeny; Editing; Cryptogene; ND8; Kinetoplast Introduction RNA editing is a process of primary transcript modifica- tion that is very widespread in nature from viruses to human. Different non-homologous mechanisms of editing indepen- dently appeared and evolved in many taxonomic groups (Chateigner-Boutin and Small 2011). For example, C → U substitutive editing is prevalent in organelles of most plants, A → I substitution editing is common among animals. In some taxonomic groups more than one type of editing can coexist. In myxomycetes C → U and U → C conversions as ∗ Corresponding author. E-mail address: aak330@yandex.ru (A.A. Kolesnikov). well as U insertions and dinucleotide insertions were found. And these mechanisms have their own separate evolutional paths (Horton and Landweber 2000). Recently a complex pattern of editing was found in the plant nucleus (Meng et al. 2010). In trypanosomatids U-insertion/deletion editing exists in the kinetoplast. The majority of genes in the kinetoplast genome are encoded in the form of cryptogenes. They do not have a functional ORF and their transcripts need to be edited by insertion/deletion of U residues before they become func- tional mRNAs. Editing is a stepwise multienzyme reaction progressing in the 3 ′ –5 ′ direction along the RNA molecule (Simpson and Maslov 1999; Stuart et al. 2005; Stuart and Panigrahi 2002). The process is mediated by short guide RNAs (gRNA) encoded mostly in the minicircles (Sturm and 0932-4739/$ – see front matter © 2011 Elsevier GmbH. All rights reserved. doi:10.1016/j.ejop.2011.09.002