Background
The intraflagellar transport (IFT) complex is an ancient protein complex that facilitates active trafficking of proteins and molecules across the eukaryotic cilium. Based on similar domain compositions Avidor-Reiss et al. (2004) and Jékely et al. (2006) postulated that the IFT originates from an ancestral proto-coatomer complex that also gave rise to vesicle coating complexes (e.g. COPI, COPII, Clathrin) and the Nuclear Pore Complex. Using comparative genomics we provide direct phylogenetic evidence of the proto-coatomer origin of the IFT.
Results
We identified the COPIα, -β2 and –ε subunits as closest paralogs to 12 IFT subunits comprising all three sub-complexes (IFT-A, -B and the BBSome). Our analysis suggests that IFT-A and the BBSome arose from an IFT-B like proto-IFT complex by intra-complex duplication of subunits. We show that the BBSome is a modular component that is lost in eukaryotic species as a precursor to ciliary loss in organisms such as fungi, apicomplexa and plants.
Conclusions
Identification of the proto-coatomer origin and subsequent evolution of the IFT complex strengthens the suspected involvement of IFT components in vesicle transport and provides a rationale for its mechanism. Expansion of ancestral subunits by duplication as well as co-evolution of specific subunits provides some insight on modularity and internal structure of the IFT complex.
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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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van Dam, J., Field, M. & Huynen, M. Origin and extension of the IFT complex in early eukaryotic evolution. Cilia 1 (Suppl 1), P56 (2012). https://doi.org/10.1186/2046-2530-1-S1-P56
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DOI: https://doi.org/10.1186/2046-2530-1-S1-P56