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

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

^*Skaggs Institute for Chemical Biology and Departments of Molecular Biology and Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037; and ^‡SmithKline Beecham Pharmaceuticals, Bioinformatics Department, 1250 South Collegeville Road, Collegeville, PA 19426-0989

Contributed by Paul R. Schimmel

Abstract

The origin of the eukaryotic cell remains an unsolved question. Numerous experimental and phylogenetic observations support the symbiotic origin of the modern eukaryotic cell, with its nucleus and (typically) mitochondria. Incorporation 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 consistent with the notion that mitochondrial genesis did not significantly precede nucleus formation. Moreover, the data raise the possibility that diplomonads are primary amitochondriates that radiated from the eukaryotic lineage before mitochondria became fully integrated as a cellular organelle.

Footnotes

↵ † Present address: Department of Chemistry, Bronfman Science Center, Williams College, Williamstown, MA 01267.
↵ § To whom reprint requests should be addressed. E-mail: lluis{at}hermes.scripps.edu.
Data deposition: The sequences presented in this paper have been deposited in the GenBank database (accession nos. AF188719, AF188717, and AF188716).
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.220388797.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.220388797
Abbreviations:

aaRS,

aminoacyl-tRNA synthetase;

AlaRS,

alanyl-tRNA synthetase