title: Expression of pair-rule gene homologues in a chelicerate: early patterning of the two-spotted spider mite Tetranychus urticae.
abstract: Embryo segmentation has been studied extensively in the fruit fly, Drosophila. These studies have demonstrated that a mechanism acting with dual segment periodicity is required for correct patterning of the body plan in this insect, but the evolutionary origin of the mechanism, the pair-rule system, is unclear. We have examined the expression of the homologues of two Drosophila pair-rule genes, runt and paired (Pax Group III), in segmenting embryos of the two-spotted spider mite (Tetranychus urticae Koch). Spider mites are chelicerates, a group of arthropods that diverged from the lineage leading to Drosophila at least 520 million years ago. In T. urticae, the Pax Group III gene Tu-pax3/7 was expressed during patterning of the prosoma, but not the opisthosoma, in a series of stripes which appear first in even numbered segments, and then in odd numbered segments. The mite runt homologue (Tu-run) in contrast was expressed early in a circular domains that resolved into a segmental pattern. The expression patterns of both of these genes also indicated they are regulated very differently from their Drosophila homologues. The expression pattern of Tu-pax3/7 lends support to the possibility that a pair-rule patterning mechanism is active in the segmentation pathways of chelicerates.
authors.affiliation: Department of Biology, University of Western Ontario, London, Canada.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Dearden
authors.forename: Cameron
authors.initials: C
authors.lastname: Donly
authors.forename: Miodrag
authors.initials: M
authors.lastname: Grbić
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001756:Blastoderm / Q000166:cytology / Q000378:metabolism; D019521:Body Patterning; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D017344:Genes, Insect; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D008845:Microinjections; D008969:Molecular Sequence Data; D009024:Morphogenesis; D009687:Nuclear Proteins; D016415:Sequence Alignment; D040102:Tetranychidae / Q000196:embryology* / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; C082157:PRRX1 protein, human; D014157:Transcription Factors; C117261:distal-less protein, insect; C489935:prd protein, Drosophila; C080833:run protein, Drosophila