even-skipped acts as a pair-rule gene in germ band stages of Tribolium development

• Published in: Developmental biology Vol. 462; no. 1; pp. 1 - 6
• Main Authors: O, Jiyun, Choe, Chong Pyo
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.2020
• Subjects: Amino Acid Sequence - genetics; Animals; Body Patterning - genetics; Embryo, Nonmammalian - metabolism; Even-skipped; Gene Expression Regulation, Developmental - genetics; Genes, Insect - genetics; Insect Proteins - genetics; Pair-rule patterning; Segmentation; Transcription Factors - metabolism; Tribolium - embryology; Tribolium - genetics; Tribolium castaneum; Tribolium castaneum; Segmentation; Even-skipped; Pair-rule patterning
• DOI: 10.1016/j.ydbio.2020.03.010
• ISSN: 0012-1606

The pair-rule gene even-skipped (eve) is essential for insect segmentation, yet its function varies among insect clades. While loss of eve results in typical pair-rule phenotypes in Drosophila, knock-down of eve orthologs shows segmental, gap-like, or asegmental phenotypes in non-Drosophila insects. In Tribolium, knock-down of the eve ortholog (Tc-eve) resulted in a graded phenotypic series ranging from strong to weak, the most informative of which was intermediate phenotypes. The strong knock-down embryos displayed asegmental phenotypes and severely disorganized germ bands which have prevented determination of Tc-eve function in later stages. In order to understand the segmentation function of Tc-eve during later germ band elongation stages, we analyzed intermediate Tc-eveRNAi embryos in which germ band elongation was less affected. Most intermediate Tc-eveRNAi germ bands displayed segmentation defects with a double segmental periodicity in the abdomen. In these intermediate embryos, Tc-engrailed (Tc-en) stripes were ectopically expanded into large bands with a double segmental periodicity, while the remaining Tc-en stripes between the expanded Tc-en stripes were absent or barely formed. The expanded Tc-en stripes seemed to be activated by primary Tc-eve stripes and Tc-paired, both of which failed to resolve into secondary segmental stripes. The absence of Tc-en stripes appeared to be a consequence of the absence of the secondary stripes of Tc-runt that were required for the activation of Tc-en stripes. These results suggest that Tc-eve functions as a pair-rule gene at least in the germ band stages of Tribolium development. •Injection of eve dsRNA causes pair-rule-like defects in Tribolium germ bands.•Primary eve stripes form in knockdown embryos but fail to resolve into segmental stripes.•Abnormal eve stripes lead to an expansion of en stripes with a double segmental periodicity.•Secondary stripes of the pair rule gene run are not maintained in the germ bands of knockdown embryos.•Absence of run stripes leads to a reduced number of en stripes.