Figure 4
From: Multiple gains of spliceosomal introns in a superfamily of vertebrate protease inhibitor genes
Intron gain in group V6 is restriced to HSP47_1 orthologues. Gene orders reveal that, with the exception of Danio rerio, non-canonical introns (symbolized by a plus sign) occur exclusively in HSP47_1 orthologues (a), but not in the paralogous HSP47_2 genes (b) or in HSP47_3 (only known from Danio rerio; not shown). Intron acquisition in HSP47_1 orthologues occurred during radiation of ray-finned fishes following divergence of the Danio rerio lineage, as suggested by lack of the extra introns in all other members of group V6, including tetrapods and lampreys.