Phylogenetic tree of inteins based on an alignment of the four protein splicing domain motifs. Phylogenetic tree based on an alignment of the four protein splicing motifs from the PRP8 inteins and the VMA inteins, together with splicing domains from inteins found in eukaryote viruses and plastids. The tree was constructed by the neighbour-joining method using PAUP*  and is a consensus derived from 1000 bootstrap replicates. The numbers indicate the percentage bootstrap support (only nodes with >50% support are shown). Accession numbers of the intein sequences are as in Figures 1 and 3 or can be obtained from InBase . S. dairenensis and S. castellii are now included in the newly described genus Naumovia; S. exiguus and S. unisporus are now included in the genus Kazachstania .