Origin of mitochondria in relation to evolutionary history of eukaryotic alanyl-tRNA synthetase

The origin of the eukaryotic cell remains an unsolved question. Numerous ex perimental and phylogenetic observations support the symbiotic origin of th e modern eukaryotic cell, with its nucleus and (typically) mitochondria, In corporation of mitochondria has been proposed to precede development of the nucleus, but it is still unclear whether mitochondria were initially part of basal eukaryotes, Data on alanyl-tRNA synthetase from an early eukaryote and other sources are presented and analyzed here. These data are consiste nt with the notion that mitochondrial genesis did not significantly precede nucleus formation. Moreover, the data raise the possibility that diplomona ds are primary amitochondriates that radiated from the eukaryotic lineage b efore mitochondria became fully integrated as a cellular organelle.