Recent gene duplications dominate evolutionary dynamics of adaptor protein complex subunits in embryophytes.

Adaptor protein complexes and the related complexes COPI and TSET function in packaging vesicles for transport among endomembrane compartments in eukaryotic cells. Differences in the complement of these complexes in lineages such as yeast and mammals as well as apicomplexan and kinetoplastid parasites via loss or duplication of subunits appears to reflect specialization in their respective trafficking systems. The model plant Arabidopsis thaliana possesses multiple paralogues for adaptor protein complex subunits, raising questions as to the timing and extent of these duplications in embryophytes (land plants). However, adaptor protein complex evolution in embryophytes is unexplored. Therefore, we analyzed genomes of diverse embryophytes and closely related green algae using extensive homology searches and phylogenetic analysis of 35 complex subunit proteins. The results reveal numerous paralogues, the vast majority of which, approximately 97%, arose from recent duplication events. This suggests that specialization of these protein complexes may occur frequently but independently in embryophytes.