Hox code in embryos of Chinese soft-shelled turtle Pelodiscus sinensis correlates with the evolutionary innovation in the turtle.
Turtles have the most unusual body plan of the amniotes, with a dorsal shell consisting of modified ribs. Because this morphological change in the ribs can be described as an axial-level specific alteration, the evolution of the turtle carapace should depend on changes in the Hox code. To identify turtle-specific changes in developmental patterns, we cloned several Hox genes from the Chinese soft-shelled turtle, Pelodiscus sinensis, examined their expression patterns during embryogenesis, and compared them with those of chicken and mouse embryos. We detected possibly turtle-specific derived traits in Hoxc-6 expression, which is restricted to the paraxial part of the embryo; in the expression of Hoxa-5 and Hoxb-5, the transcripts of which were detected only at the cervical level; and in Hoxc-8 and Hoxa-7 expression, which is shifted anteriorly relative to that of the other two amniote groups. From the known functions of the Hox orthologs in model animals, these P. sinensis-specific changes apparently correlate with specializations in the turtle-specific body plan.
Ohya
Yoshie Kawashima
YK
Laboratory for Evolutionary Morphology, Center for Developmental Biology (CDB), RIKEN, Kobe 650-0047, Japan.
Kuraku
Shigehiro
S
Kuratani
Shigeru
S
D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics*; D002642:Chick Embryo; D003001:Cloning, Molecular; D016000:Cluster Analysis; D018076:DNA, Complementary / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D019170:Somites / Q000166:cytology / Q000378:metabolism*; D014426:Turtles / Q000033:anatomy & histology* / Q000196:embryology* / Q000235:genetics
D018076:DNA, Complementary; D018398:Homeodomain Proteins