Reconstructing evolutionary relationships from functional data: a consistent classification of organisms based on translation inhibition response

Abstract

The last two decades have witnessed an unsurpassed effort aimed at reconstructing the history of life freom the genetic information contained in extant organisms. The availability of many sequenced genomes has allowed the reconstruction of phylogenies freom gene families and its comparison with traditional singlegene trees. However, the appearance of major discrepancies between both approaches questions whether horizontal gene transfer (HGT) has played a prominent role in shaping the topology of the Tree of Life. Recent attempts at solving this controversy and reaching a consensus tree combine molecular data with additional phylogenetic markers. Translation is a universal cellular function that involves a meaningful, highly conserved set of genes: both rRNA and rprotein operons have an undisputed phylogenetic value and rarely undergo HGT. Ribosomal function reflects the concerted expression of that genetic network and consequently yields information about the evolutionary paths followed by the organisms. Here we report on tree reconstruction using a measure of the performance of the ribosome: antibiotic sensitivity of protein synthesis. A large database has been used where 33 ribosomal systems belonging to the three major cellular lineages were probed against 38 protein synthesis inhibitors. Different definitions of distance between pairs of organisms have been explored, and the classical algorithm of bootstrap evaluation has been adapted to quantify the reliability of the reconstructions obtained. Our analysis returns a consistent phylogeny, where archaea are systematically affiliated to eukarya, in agreement with recent reconstructions which used informationprocessing systems. The integration of the information derived freom relevant functional markers into current phylogenetic reconstructions might facilitate achieving a consensus Tree of Life. (C) 2004 Elsevier Inc. All rights reserved.