title: Vasa expression and germ-cell specification in the spider mite Tetranychus urticae.
abstract: The specification of germ cells is an important process during the development of all animals. Expression of an evolutionarily conserved gene such as vasa can be used as a marker for germ cell fate. We have isolated a vasa-related gene from the two-spotted spider mite (Tetranychus urticae) and used it to examine the segregation of germ cells in this animal. In spider mites, vasa expression first appears in a group of cells that do not join the initial blastoderm surface. Instead, these cells remain in the interior of the blastoderm and then migrate to posterior regions of the embryo, where they form a cluster that appears in regions of the embryo consistent with the gonads. The expression pattern of this spider mite vasa homologue implies a novel process acts to specify germ cells in this species and that the specification of germ cells is an evolutionarily labile process.
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, N6A 5B7, Canada. peter.dearden@stonebow.otago.ac.nz
authors.forename: Peter
authors.initials: P
authors.lastname: Dearden
authors.forename: Miodrag
authors.initials: M
authors.lastname: Grbic
authors.forename: Cam
authors.initials: C
authors.lastname: Donly
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001756:Blastoderm / Q000166:cytology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D005854:Germ Cells / Q000502:physiology*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D008925:Mites / Q000145:classification / Q000196:embryology* / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D019476:Insect Proteins; D020365:RNA Helicases