title: Caudal regulates the spatiotemporal dynamics of pair-rule waves in Tribolium.
abstract: In the short-germ beetle Tribolium castaneum, waves of pair-rule gene expression propagate from the posterior end of the embryo towards the anterior and eventually freeze into stable stripes, partitioning the anterior-posterior axis into segments. Similar waves in vertebrates are assumed to arise due to the modulation of a molecular clock by a posterior-to-anterior frequency gradient. However, neither a molecular candidate nor a functional role has been identified to date for such a frequency gradient, either in vertebrates or elsewhere. Here we provide evidence that the posterior gradient of Tc-caudal expression regulates the oscillation frequency of pair-rule gene expression in Tribolium. We show this by analyzing the spatiotemporal dynamics of Tc-even-skipped expression in strong and mild knockdown of Tc-caudal, and by correlating the extension, level and slope of the Tc-caudal expression gradient to the spatiotemporal dynamics of Tc-even-skipped expression in wild type as well as in different RNAi knockdowns of Tc-caudal regulators. Further, we show that besides its absolute importance for stripe generation in the static phase of the Tribolium blastoderm, a frequency gradient might serve as a buffer against noise during axis elongation phase in Tribolium as well as vertebrates. Our results highlight the role of frequency gradients in pattern formation.
authors.affiliation: Genetics Program, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: Ezzat
authors.initials: E
authors.lastname: El-Sherif
authors.affiliation: Division of Biology, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Division of Biology, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: Jinping
authors.initials: J
authors.lastname: Fu
authors.affiliation: Division of Biology, Kansas State University, Manhattan, Kansas, United States of America.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Brown
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D014231:Tribolium / Q000196:embryology* / Q000235:genetics*
chemical_list: D019476:Insect Proteins