Headless class XI myosins. A) Headless myosins of subtype myosin-11E2 were identified in Arabidopsis thaliana and Eutrema halophilum (NCBI assembly). These myosins are subtype myosin-11E duplicates, which have lost the myosin head domains or were derived by partial duplication of the myosin-11E tail domains. Gene structures and domain architectures of Arabidopsis thaliana (At) myosin-11E and myosin-11E2 are shown for comparison. Exons 1 to 22 and exons 27 and 28 (encoding the unique region) of AtMyo11E have been lost in AtMyo11E2, resulting in the loss of all domains but the coiled-coil and DIL domains. Below the gene structure schemes, an alignment of the gene structures is given, in which exonic sequences are represented by hyphens ("-") and introns by vertical bars ("|"). Most introns of both sequences have the same position and phase demonstrating their common ancestry. B) Headless myosins of subtype 11E4 are found in all members of the Poales clade. For instance, Sorghum bicolor (Sob) myosin-11E4 lost exons 1 to 20 and exon 23 compared to SobMyo11E3. Therefore, subtype 11E4 myosins encode only 3 IQ motifs and miss part of the coiled-coil region. Gene structure conservation and loss of the intron between exons 35 and 36 (11E3 numbering) in myosin-11E4 is shown in the exon-intron pattern below the gene structures. Differences in the domain architectures of subtype 11E3 and headless 11E4 myosins are highlighted in the domain organisation scheme and the multiple sequence alignment. In this alignment, residues encoded by exons 20 and 21 of SobMyo11E1, SobMyo11E2, and SobMyo11E3 were aligned with those encoded by exons 1 and 2 of headless myosin-11E4 from Zea mays B73 (ZmMyo11E4), Sorghum bicolor (SobMyo11E4), Brachyopodium distachyon (BdMyo11E4) and Oryza sativa indica group (Os_bMyo11E4). Below the sequences, yellow lines and red bars indicate exons and IQ motifs, respectively.
Mühlhausen and Kollmar BMC Evolutionary Biology 2013 13:202 doi:10.1186/1471-2148-13-202