Aspects of dorso‐ventral and proximo‐distal limb patterning in onychophorans. Issue 1 (January 2015)

• Record Type: Journal Article
• Authors: Janssen, Ralf; Jörgensen, Mette; Prpic, Nikola‐Michael; Budd, Graham E.
• Is Part Of: Evolution & development. Volume 17:Issue 1(2015)
• Page Start: 21
• Page End: 33
• Publication Date: 2015-01
• Subjects: Evolution (Biology) -- Periodicals; Developmental biology -- Periodicals; 576.82
• DOI: 10.1111/ede.12107
• Languages: English
• ISSNs: 1520-541X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>SUMMARY</title> <sec id="ede12107-sec-0001" sec-type="section"> <p>Onychophorans (velvet worms) are closely related to the arthropods, but their limb morphology represents a stage before arthropodization (i.e., the segmentation of the limbs). We investigated the expression of onychophoran homologs of genes that are involved in dorso‐ventral (DV) and proximo‐distal (PD) limb patterning in arthropods. We find that the two onychophoran <italic>optomotor‐blind</italic> (<italic>omb</italic>) genes, <italic>omb‐1</italic> and <italic>omb‐2</italic>, are both expressed in conserved patterns in the dorsal ectoderm of the limbs, including the onychophoran antennae (the frontal appendages). Surprisingly, the expression of <italic>decapentaplegic</italic> (<italic>dpp</italic>), which acts upstream of <italic>omb</italic> in <italic>Drosophila</italic>, is partially reversed in onychophoran limbs compared to its expression in arthropods. A conserved feature of <italic>dpp</italic> expression in arthropods and onychophorans, however, is the prominent expression of <italic>dpp</italic> in the tips of developing limbs, which, therefore, may represent the ancestral pattern. The expression patterns of <italic>wingless</italic> (<italic>wg</italic>) and <italic>H15</italic> are very diverged in onychophorans. The <italic>wg</italic> gene is only expressed in the limb tips and the single <italic>H15</italic> gene is expressed in a few dorsal limb cells, but not on the ventral side. The expression of <italic>wg</italic> and <italic>dpp</italic> at the limb tips is one of the three possible alternatives predicted by the topology model of arthropod limb patterning and is, thus, compatible with a conserved function of <italic>wg</italic> and <italic>dpp</italic> in the patterning of the PD axis. On the other hand, DV limb gene expression is less conserved, and the specification of ventral fate appears to involve neither <italic>wg</italic> nor <italic>H15</italic> expression.</p> </sec> </abstract>