title: Loss of Tc-arrow and canonical Wnt signaling alters posterior morphology and pair-rule gene expression in the short-germ insect, Tribolium castaneum.
abstract: Wnt signaling has been implicated in posterior patterning in short-germ insects, including the red flour beetle Tribolium castaneum (Bolognesi et al. Curr Biol 18:1624-1629, 2008b; Angelini and Kaufman Dev Biol 283:409-423, 2005; Miyawaki et al. Mech Dev 121:119-130, 2004). Specifically, depletion of Wnt ligands Tc-Wnt1 and Tc-WntD/8 produces Tribolium embryos lacking abdominal segments. Similar phenotypes are produced by depletion of Tc-porcupine (Tc-porc) or Tc-pangolin (Tc-pan), indicating that the signal is transmitted through the canonical Wnt pathway (Bolognesi et al. Curr Biol 18:1624-1629, 2008b). Here we show that RNAi for the receptor Tc-arrow produced similar truncated phenotypes, providing additional evidence supporting canonical signal transduction. Furthermore, since in Tribolium segments are defined sequentially by a pair-rule gene circuit that, when interrupted, produces truncated phenotypes (Choe et al. Proc Natl Acad Sci U S A 103:6560-6564, 2006), we investigated the relationship between loss of Wnt signaling and this pair-rule gene circuit. After depletion of the receptor Tc-arrow, expression of Tc-Wnt1 was noticeably absent from the growth zone, while Tc-WntD/8 was restricted to a single spot of expression in what remained of the posterior growth zone. The primary pair-rule genes Tc-runt (Tc-run) and Tc-even-skipped (Tc-eve) were expressed normally in the anterior segments, but were reduced to a single spot in the remnants of the posterior growth zone. Thus, expression of pair-rule genes and Tc-WntD/8 are similarly affected by depletion of Wnt signal and disruption of the posterior growth zone.
authors.affiliation: Division of Biology, Ackert Hall, Kansas State University, Manhattan, KS 66502, USA.
authors.forename: Renata
authors.initials: R
authors.lastname: Bolognesi
authors.forename: Tamara D
authors.initials: TD
authors.lastname: Fischer
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Brown
mesh_terms: D000818:Animals; D019521:Body Patterning; D004625:Embryo, Nonmammalian / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction; D014231:Tribolium / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D019476:Insect Proteins; D051153:Wnt Proteins
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