title: Krüppel acts as a gap gene regulating expression of hunchback and even-skipped in the intermediate germ cricket Gryllus bimaculatus.
abstract: In Drosophila, a long germ insect, segmentation occurs simultaneously across the entire body. In contrast, in short and intermediate germ insects, the anterior segments are specified during the blastoderm stage, while the remaining posterior segments are specified during later stages. In Drosophila embryos, the transcriptional factors coded by gap genes, such as Krüppel, diffuse in the syncytial environment and regulate the expression of other gap, pair-rule, and Hox genes. To understand the segmentation mechanisms in short and intermediate germ insects, we investigated the role of Kr ortholog (Gb'Kr) in the development of the intermediate germ insect Gryllus bimaculatus. We found that Gb'Kr is expressed in a gap pattern in the prospective thoracic region after cellularization of the embryo. To determine the function of Gb'Kr in segmentation, we analyzed knockdown phenotypes using RNA interference (RNAi). Gb'Kr RNAi depletion resulted in a gap phenotype in which the posterior of the first thoracic through seventh abdominal segments were deleted. Analysis of the expression patterns of Hox genes in Gb'Kr RNAi embryos indicated that regulatory relationships between Hox genes and Kr in Gryllus differ from those in Oncopeltus, another intermediate germ insect. Furthermore, we found that Gb'Kr regulates expression minimally of hunchback and even-skipped, directly or indirectly, in the prospective thoracic region. Our findings suggest that Gb'Kr is a gap gene that acts in the cellular environment and is required for segmentation in the thoracic and abdominal regions through the regulation of gap and pair-rule gene expression.
authors.affiliation: Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, 2-1 Minami-Jyosanjima-cho, Tokushima City 770-8506, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Mito
authors.forename: Haruko
authors.initials: H
authors.lastname: Okamoto
authors.forename: Wakako
authors.initials: W
authors.lastname: Shinahara
authors.forename: Yohei
authors.initials: Y
authors.lastname: Shinmyo
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Miyawaki
authors.forename: Hideyo
authors.initials: H
authors.lastname: Ohuchi
authors.forename: Sumihare
authors.initials: S
authors.lastname: Noji
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D006135:Gryllidae / Q000033:anatomy & histology / Q000196:embryology / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D017403:In Situ Hybridization; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology
chemical_list: D018398:Homeodomain Proteins; D019476:Insect Proteins; D051741:Kruppel-Like Transcription Factors