HEATR2 Plays a Conserved Role in Assembly of the Ciliary Motile Apparatus
Figure 5
CG31320/HEATR2 is conserved in eukaryotes with motile cilia/flagella and its associated axonemal dynein apparatus.
CG31320/HEATR2 orthologues are found in species with cilia/flagella that have motile function and retain elements of the axonemal dyneins required for this motility. Species which have no cilia (ie. amoebozoans, flowering plants, yeast) or those which lack motile cilia (i.e. nematodes) have lost HEATR2 orthologues as well as the axonemal dynein genes. Interestingly, unusual species with variant motility programmes still retain HEATR2 orthologues. These include T. pseudonana whose male gametes have motile axonemes without inner arm dyneins, and P. patens, whose male gametes have motile flagella without outer arm dyneins. Similarly, P. falciparum which assembles its flagella intracytosolically through an IFT-independent programme, retains a HEATR2 orthologue. This suggests CG31320/HEATR2 is an essential element of an ancient programme required for ciliary/flagellar motility. This figure is a summary of a more extensive search detailed in Table S1 for CG31320/HEATR2 orthologues as well as axonemal dynein components of the outer (ODA) and inner (IDA) dynein arms, as summarized in columns. Filled circles: orthologues as determined by the top score in reciprocal BLASTP or TBLASTN searches. Open circle: no homologue present. Half-filled circle: evidence supporting existence of at least one orthologue per category as analyzed in Table S1 by reciprocal BLASTP or TBLASTN searches. Information for the intraflagellar transport (IFT) pathway built upon Wickstead and Gull (2007) with our own searches for IFT components by reciprocal BLASTP or TBLASTN searches.