In euryarchaeal methanogen M.kandleri and in Nanoarchaea N. equitans some of the missing tRNA genes are embedded in others. We argue from bioinformatic evidence that position specific intron splicing is the key behind co-location of these tRNA genes.
Cite
@article{arxiv.q-bio/0509026,
title = {Embedded transfer RNA Genes},
author = {Zhumur Ghosh and Smarajit Das and Jayprokas Chakrabarti and Bibekanand Mallick and Satyabrata Sahoo},
journal= {arXiv preprint arXiv:q-bio/0509026},
year = {2007}
}