Abstract
BackgroundSox (Sry-related high-mobility-group box) genes represent important factors in animal development. Relatively little, however, is known about the embryonic expression patterns and thus possible function(s) of Sox genes during ontogenesis in panarthropods (Arthropoda+Tardigrada+Onychophora). To date, studies have been restricted exclusively to higher insects, including the model system Drosophila melanogaster, with no comprehensive data available for any other arthropod group, or any tardigrade or onychophoran.ResultsThis study provides a phylogenetic analysis of panarthropod Sox genes and presents the first comprehensive analysis of embryonic expression patterns in the flour beetle Tribolium castaneum (Hexapoda), the pill millipede Glomeris marginata (Myriapoda), and the velvet worm, Euperipatoides kanangrensis (Onychophora). 24 Sox genes were identified and investigated: 7 in Euperipatoides, 8 in Glomeris, and 9 in Tribolium. Each species possesses at least one ortholog of each of the five expected Sox gene families, B, C, D, E, and F, many of which are differentially expressed during ontogenesis.ConclusionSox gene expression (and potentially function) is highly conserved in arthropods and their closest relatives, the onychophorans. Sox B, C and D class genes appear to be crucial for nervous system development, while the Sox B genes Dichaete (D) and Sox21b likely play an additional conserved role in panarthropod segmentation. The Sox B gene Sox21a likely has a conserved function in foregut and Malpighian tubule development, at least in Hexapoda. The data further suggest that Sox D and E genes are involved in mesoderm differentiation, and that Sox E genes are involved in gonadal development.The new data expand our knowledge about the expression and implied function of Sox genes to Mandibulata (Myriapoda+Pancrustacea) and Panarthropoda (Arthropoda+Onychophora).
Highlights
Sox (Sry-related high-mobility-group box) genes represent important factors in animal development
Panarthropods possess a conserved complement of Sox genes representing at least one member of each Sox gene family, Sox B, Sox C, Sox D, Sox E and Sox F
The provided comprehensive gene expression analysis suggests a high degree of evolutionary conservation, in which Sox B class genes are generally involved in neurogenesis, and in which the Sox B class gene Dichaete is likely involved in segmentation
Summary
Sox (Sry-related high-mobility-group box) genes represent important factors in animal development. Sox classes G, H, I and J are lineage specific: SoxG is vertebrate specific, SoxH is specific for humans, SoxI is only found in the frog Xenopus laevis, and SoxJ is specific for the nematode Caenorhabditis elegans (Bowles et al [8], Ito et al [9]) Despite their ubiquity among metazoans and their acknowledged importance for key developmental processes, Sox genes have not been investigated in any arthropod other than the vinegar fly Drosophila melanogaster (Cremazy et al [10], McKimmie et al [11]), or even in any other ecdysozoan species with the exception of Caenorhabditis elegans (Vidal et al [12]). A study investigating content and expression of Sox genes in the common house spider Parasteatoda tepidariorum has been submitted to BMC Evolutionary Biology (Paese et al [17])
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