Poster abstracts
Poster number 123 submitted by Brandon Iwaniec
Surveying tRNA introns across eukaryotes and archaea: The intron of Tyr-GUA tRNA is conserved from the last common ancestor of all eukaryotes, but some species lack all tRNA introns
Brandon W. J. Iwaniec (Department of Molecular Genetics, The Ohio State University ), Ambro van Hoof (Department of Molecular Genetics, The Ohio State University )
Abstract:
The existence of tRNAs containing introns is thought to be universal throughout eukaryotes. Our recent work shows that within metazoan specifically, introns in Tyr-GUA, Ile-UAU, and Leu-CAA tRNAs are very prevalent, while other tRNAs largely lack introns. We also showed that some nematode species of the superfamily Diplogasteroidea have lost introns in Tyr-GUA and Ile-UAU tRNAs, and one of those, Levipalatum texanum, has lost all tRNA introns. The lack of introns in L. texanum is accompanied by the absence of the tRNA endonuclease, one of the two enzymes required for tRNA splicing. Here we expand on this work by more broadly studying the distribution of tRNA introns. We analyzed available genomes spanning 119 Nematoda genera. We found that species of the infraorder Tylenchomorpha are missing the intron in Ile-UAU tRNA but retain introns in Tyr-GUA and Leu-CAA tRNAs. The Diplogasteroidea and Tylenchomorpha are both in the suborder Rhabditina, but it is unclear why intron loss would be more prevalent in this suborder than in other nematodes, or why Levipalatum was able to lose all tRNA introns, which are otherwise very conserved. Further analysis of the Nematoda tRNAs revealed that L. texanum Leu-CAA contains a unique basepair mismatch in the anticodon stem. We also examined tRNA intron conservation in early branching eukaryotes and archaea. While introns in Tyr-GUA, Ile-UAU, and Leu-CAA tRNAs are prevalent in animals, only Tyr-GUA tRNA contained introns in most early branching eukaryotes. Two early branching eukaryotes, one in the Fornicata and one in the Stramenopila, contained no predicted tRNA introns nor homologs of tRNA endonuclease, while other Fornicate and Stramenopila did. The conservation of the Tyr-GUA tRNA intron in Archaea appears to be class specific, rather than sporadic across the four kingdoms. These analyses indicate that the intron of Tyr-GUA tRNA is conserved from the last common ancestor of all eukaryotes and therefore must have an important function, but that in at least three branches of the eukaryotic tree all tRNA introns and the tRNA endonuclease were lost.
Keywords: tRNA introns