Kruppel is a gap gene in the intermediate germband insect Oncopeltus fasciatus and is required for development of both blastoderm and germ band-derived segments

Segmentation in long germband insects such as Drosophila occurs essentially simultaneously across the entire body. A cascade of segmentation genes patterns the embryo along its anterior-posterior axis via subdivision of the blastoderm. This is in contrast to short and intermediate germband modes of segmentation where the anterior segments are formed during the blastoderm stage and the remaining posterior segments arise at later stages from a posterior growth zone. The biphasic character of segment generation in short and intermediate germ insects implies that different formative mechanisms may be operating in blastoderm-derived and germband-derived segments. In Drosophila, the gap gene Kruppel is required for proper formation of the central portion of the embryo. This domain of Kruppel activity in Drosophila corresponds to a region that in short and intermediate germband insects spans both blastoderm, and germband-derived segments. We have cloned the Kruppel homolog from the milkweed bug, Oncopeltus fasciatus (Hemiptera, Lygaeidae), an intermediate germband insect. We find that Oncopeltus Kruppel is expressed in a gap-like domain in the thorax during the blastoderm and germband stages of embryogenesis. In order to investigate the function of Kruppel in Oncopeltus segmentation, we generated knockdown phenotypes using RNAi. Loss of Kruppel activity in Oncopeltus results in a large gap phenotype, with loss of the mesothoracic through fourth abdominal segments. Additionally, we find that Kruppel is required to suppress both anterior and posterior Hox gene expression in the central portion of the germband. Our results show that Kruppel is required for both blastoderm-derived and germband-derived segments and indicate that Kruppel function is largely conserved in Oncopeltus and Drosophila despite their divergent embryogenesis.