The Non-LTR Retrotransposon R2 in Termites (Insecta, Isoptera): Characterization and Dynamics

Abstract

The full-length element of the non-LTR retrotransposon R2 is here characterized in three European isopteran species: the more primitive Kalotermes flavicollis (Kalotermitidae), including two highly divergent mitochondrial lineages, and the more derived Reticulitermes lucifugus and R. urbis (Rhinotermitidae). Partial 3' sequences for R. grassei and R. balkanensis were also analyzed. The essential structural features of R2 elements are conserved in termites. Phylogenetic analysis revealed that termite elements belong to the same clade and that their phylogeny is fully compatible with the phylogeny of their host species. The study of the number and the frequency of R2 insertion variants in four R. urbis colonies suggests a greatly reduced, or completely absent, recent element activity.

Non-LTR R2 Element Evolutionary Patterns: Phylogenetic Incongruences, Rapid Radiation and the Maintenance of Multiple Lineages

“…clade [18], ii ) the European Notostraca clade (genera Triops and Lepidurus ) [21], iii ) the hard ticks clade [20] and iv ) the Reticulitermes termites clade [19].…”

“…Presently identified R2s were then gathered in a single dataset with all elements available from literature (Eickbush lab, http://blogs.rochester.edu/EickbushLab/?page_id=602; [5], [13], [19], [20], [21]; Table S1). R8 and R9 elements, closely related to R2 [1], [2], have been also included in phylogenetic analyses.…”

“…Only in few instances a pattern of strict vertical inheritance occurs: it happens for the insect genera Drosophila and Reticulitermes , the Ixodida ticks and the crustacean genus Lepidurus [18], [19], [20], [21]. As a general remark, though, it is to be pointed out that, even if the main topology can be recognized, trees are weakly supported in most instances [1], [2], [13], [16], [20], [21].…”

Processing and Translation Initiation of Non-long Terminal Repeat Retrotransposons by Hepatitis Delta Virus (HDV)-like Self-cleaving Ribozymes

“…These included additional A. gambiae RTEs, the JAM1/RTE (28) in the yellow fever mosquito Aedes aegypti, the telomeric R1-like repeat element SARTPx2 (10,11) in the Asian swallowtail butterfly Papilio xuthus, and Baggins retrotransposons in a number of Drosophila species. Ribozymes were also found at 5Ј termini of many rDNA-targeting retrotransposons as follows: the R2 element in Drosophila; the termites Kalotermes flavicollis and Reticulitermes lucifugus (29), the sea squirt Ciona intestinalis (30), the black-legged tick Ixodes scapularis (GenBank accession number ABJB010506112), the horseshoe shrimp Triops cancriformis (GenBank accession number ABJB010506112), and the Zebra finch Taeniopygia guttata (20); the R4 elements (9) in the human intestinal roundworm Ascaris lumbricoides and the horse intestinal roundworm Parascaris equorum; and R6Ag1 and R6Ag3 elements (11) in A. gambiae. Partial ribozymes, missing only the 5Ј strand of P1, were found in R2 elements of the European earwig Forficula auricularia (16), the Atlantic horseshoe crab Limulus polyphemus (16,31) and the fly Rhynchosciara americana (32).…”

Integration, Regulation, and Long-Term Stability of R2 Retrotransposons

“…Interestingly, variation in the ability of an organism to transcribe a region of the rDNA locus free of R2 insertions can explain why species have very different percentages of their rDNA units inserted with R2 (10,27,31,121,122). If an organism is less capable at differentiating between inserted and uninserted rDNA units, than all R2 inserts are potentially harmful and will be selected against.…”