Figure 5: An evolutionary history of the fungal TER intron.
From: Prevalent and distinct spliceosomal 3′-end processing mechanisms for fungal telomerase RNA
The AU/AG intron is predominate and basal (thick blue line) among fungal TER introns. The GU/AG or AU/AC (U1/U2-type) introns (orange) are the putative predecessor of the fungal TER AU/AG intron with only a single point mutation (red) in either intron necessary to convert into this intron type (dashed red lines). From this putative ancestral fungal TER AU/AG intron, the TER GU/AG type intron appears to have arisen twice independently (purple). A subgroup of budding yeasts has lost TER spliceosomal cleavage.
