Abstract
BackgroundEFL (or elongation factor-like) is a member of the translation superfamily of GTPase proteins. It is restricted to eukaryotes, where it is found in a punctate distribution that is almost mutually exclusive with elongation factor-1 alpha (EF-1α). EF-1α is a core translation factor previously thought to be essential in eukaryotes, so its relationship to EFL has prompted the suggestion that EFL has spread by horizontal or lateral gene transfer (HGT or LGT) and replaced EF-1α multiple times. Among green algae, trebouxiophyceans and chlorophyceans have EFL, but the ulvophycean Acetabularia and the sister group to green algae, land plants, have EF-1α. This distribution singles out green algae as a particularly promising group to understand the origin of EFL and the effects of its presence on EF-1α.ResultsWe have sampled all major lineages of green algae for both EFL and EF-1α. EFL is unexpectedly broad in its distribution, being found in all green algal lineages (chlorophyceans, trebouxiophyceans, ulvophyceans, prasinophyceans, and mesostigmatophyceans), except charophyceans and the genus Acetabularia. The presence of EFL in the genus Mesostigma and EF-1α in Acetabularia are of particular interest, since the opposite is true of all their closest relatives. The phylogeny of EFL is poorly resolved, but the Acetabularia EF-1α is clearly related to homologues from land plants and charophyceans, demonstrating that EF-1α was present in the common ancestor of the green lineage.ConclusionThe distribution of EFL and EF-1α in the green lineage is not consistent with the phylogeny of the organisms, indicating a complex history of both genes. Overall, we suggest that after the introduction of EFL (in the ancestor of green algae or earlier), both genes co-existed in green algal genomes for some time before one or the other was lost on multiple occasions.
Highlights
EFL is a member of the translation superfamily of GTPase proteins
Results & discussion Characterisation of new EFL and EF-1α genes from green algae Previously, EFL was found in a number of species of chlorophyceans and trebouxiophyceans, but not in any land plants or the ulvophycean A. acetabulum
This lead to the conclusion that it originated in a common ancestor of chlorophyceans and trebouxiophyceans [13], which in turn leads to the prediction that all other green algae should only contain EF-1α
Summary
EFL (or elongation factor-like) is a member of the translation superfamily of GTPase proteins. EF-1α is a core translation factor previously thought to be essential in eukaryotes, so its relationship to EFL has prompted the suggestion that EFL has spread by horizontal or lateral gene transfer (HGT or LGT) and replaced EF-1α multiple times. Horizontal or lateral gene transfer (HGT or LGT) is the non-sexual movement of genetic information between two species This process has been amply documented to affect prokaryotic genomes: the frequency and importance of such events is debated, there is little debate that it plays some role [1,2,3,4]. There is generally a mutually exclusive distribution of EFL and EF-1α, and both are scattered around the tree of eukaryotes. Based on the current distribution we favour the movement of EFL between eukaryotes, but this must be reassessed as the distribution becomes better known
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