MBE Advance Access originally published online on May 13, 2008
Molecular Biology and Evolution 2008 25(8):1526-1529; doi:10.1093/molbev/msn113
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Letters |
The Guanine Nucleotide Exchange Factors Sec2 and PRONE: Candidate Synapomorphies for the Opisthokonta and the Archaeplastida
Department of Botany and Department of Philosophy and History of Science, Faculty of Sciences, Charles University in Prague, Prague, Czech Republic
E-mail: melias{at}natur.cuni.cz.
Accepted for publication May 7, 2008.
Although recent multigene phylogenetic analyses support close relationship of Metazoa and Fungi (the eukaryotic supergroup Opisthokonta) and monophyly of eukaryotes with the primary plastid, that is, Chloroplastida, Rhodophyta, and Glaucophyta (the supergroup Archaeplastida or Plantae), some authors still challenge this scheme. I found that 2 particular types of guanine nucleotide exchange factors (GEFs, i.e., cofactors of GTPases) might provide a new piece of evidence to resolve this controversy. An exhaustive analysis of available sequence data revealed that Sec2-related proteins, known to serve as GEF for exocytic GTPases of the Rab8/Sec4 subfamily, are restricted to opisthokonts, whereas proteins with the PRONE domain, recently described as novel plant-specific GEFs for RHO family GTPases, occur only in Chloroplastida and Rhodophyta. The results thus point to possible evolutionary innovations in the exocytic apparatus of the ancestral opisthokonts and reveal the probably first plastid-independent trait (i.e., a unique mode of RHO GTPase regulation) exclusive for Chloroplastida + Rhodophyta, further supporting monophyly of these 2 groups.
Key Words: GTPases eukaryotes phylogeny Opisthokonta Archaeplastida
Andrew Roger, Associate Editor