Evolutionary conservation of ciliary proteins in non-ciliated plants

During evolution, when a trait is lost, the genes encoding proteins required for that trait can either be lost, be co-opted to a novel role, or be retained for alternative roles. Cilia, organelles used in many eukaryotic species for motility and sensing, are a model for studying such evolutionary scenarios as they have been lost independently multiple times.

The land plants provide a good example of such loss in that basal land plants have the ability to produce cilia, but cilia have been lost at least twice in the lineage – once at the base of the flowering plants, and once within gymnosperms.

In a new study, a team of researchers  from the University of Oxford and the University of Nottingham, described an approach that uses phylogenetic profiling to identify a core set of ciliary function proteins.  The research report was published on December 30, 2011 in the scholarly open access journal BMC Plant Biology.

Direct fluorescence of whole cell Trypanosoma brucei showing cellular localisation of TbFBB17 (Tb10.406.0130) N-terminal YPF chimera (left panel) and an overlay of signal from YFP (green), DAPI (magenta) and phase-contrast (right panel). Tb10.406.0130 localises to the flagellum (white arrow).  Image credit and copyright: Dr. Matthew E Hodges, University of Oxford.

The researchers analyzed the distribution of orthologuos proteins encoded in the genomes of 45 species.

By combining a trait map with genomic data, insight can be provided into the possible ciliary roles of specific genes, and genes with evolutionarily conserved roles across diverse species can be identified. The results of such studies reinforce the expectation that there are a number of conserved ciliary proteins present across ciliated species, and that the majority of ciliary proteins are lost when cilia are lost.

"Remarkably, however, this bioinformatic approach also showed that many genes with a demonstrable ciliary role in ciliated species are maintained in non-ciliated flowering land plants," said first author Dr Matthew Hodges. The study provided a unique candidate list of genes that can be used to investigate evolutionary scenarios of sub- and neo-functionalisation, and to understand basic evolutionary principles.

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