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Gene expression patterns in an onychophoran reveal that regionalization predates limb segmentation in pan‐arthropods
Author(s) -
Janssen Ralf,
Eriksson Bo Joakim,
Budd Graham E.,
Akam Michael,
Prpic NikolaMichael
Publication year - 2010
Publication title -
evolution and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.651
H-Index - 78
eISSN - 1525-142X
pISSN - 1520-541X
DOI - 10.1111/j.1525-142x.2010.00423.x
Subject(s) - biology , appendage , anatomy , evolutionary biology , arthropod , chordate , drosophila melanogaster , clade , gene , phylogenetics , genetics , vertebrate , paleontology
SUMMARY In arthropods, such as Drosophila melanogaster , the leg gap genes homothorax ( hth ), extradenticle ( exd ), dachshund ( dac ), and Distal‐less ( Dll ) regionalize the legs in order to facilitate the subsequent segmentation of the legs. We have isolated homologs of all four leg gap genes from the onychophoran Euperipatoides kanangrensis and have studied their expression. We show that leg regionalization takes place in the legs of onychophorans even though they represent simple and nonsegmented appendages. This implies that leg regionalization evolved for a different function and was only later co‐opted for a role in leg segmentation. We also show that the leg gap gene patterns in onychophorans (especially of hth and exd ) are similar to the patterns in crustaceans and insects, suggesting that this is the plesiomorphic state in arthropods. The reversed hth and exd patterns in chelicerates and myriapods are therefore an apomorphy for this group, the Myriochelata, lending support to the Myriochelata and Tetraconata clades in arthropod phylogeny.