Krüppel-homolog is essential for the coordination of regulatory gene hierarchies in early Drosophila development

Abstract

Drosophila development is marked by two major morphogenetic processes: embryogenesis and metamorphosis. While insect metamorphosis is known to be controlled by the steroid hormone ecdysone, relatively little is known concerning the hormonal control of embryogenesis. Here we show that many ecdysone-regulated transcripts of metamorphosis are also expressed in a wavelike manner during embryogenesis, suggesting that these genes also participate in an embryonic ecdysone response. At metamorphosis, the Krüppel-homolog (Kr-h) gene, coding for a zinc finger protein, is required during the prepupal ecdysone response. Kr-h mutants die at the prepupal-pupal transition. In these mutants, the expression of several ecdysone-regulated genes is disrupted and we concluded that Kr-h was a key modulator of the hormonal response [Dev. Biol. 221 (2000) 53]. While Kr-h is expressed in many tissues at metamorphosis, in embryos expression is restricted to neurons. Here, we investigate its role during early Drosophila development using new alleles with an earlier lethality than those previously described. Although we detect only minor morphological defects in these mutants, we show that Kr-h expression is necessary for the early development of Drosophila and that, during metamorphosis, Kr-h acts as a modulator of the expression of many of these ecdysone-regulated genes.

Roles of Drosophila Kruppel‐homolog 1 in neuronal morphogenesis

“…Fly strains used in this study include (1) Kr-h1[1]/CyO-GFP (Beck et al, 2004); (2) EP2289 (Kraut et al, 2001); (3) GAL4-201Y (Yang et al, 1995); (4) GAL4-OK107 (Connolly et al, 1996); (5) 247-GAL4 (McGuire et al, 2001); (6) ato-GAL4 (Hassan et al, 2000); (7) tubP-GAL80[ts] (McGuire et al, 2003); (8) UAS-mCD8::GFP ; (9) FRT40A,Kr-h1[1]/CyO; (10) FRT40A/CyO; (11) hs-FLP,UAS-mCD8::GFP;FRT40A,tubP-GAL80;GAL4-OK107; (12) FRT19A,usp[2]/FM7; (13) hs-FLP,tubP-GAL80,FR-T19A;UAS-mCD8::GFP;GAL4-OK107; (14) FRTG13,babo[9],UAS-mCD8::GFP/CyO (Zheng et al, 2006) …”

“…The rabbit polyclonal anti-KR-H1 Ab (Beck et al, 2004), AD4.4 mAb (for detecting EcR-B1; Talbot et al, 1993), BP106 mAb, 1D4 mAb, and anti-mCD8 mAb were used at 1:1000, 1:20, 1:50, 1:50, and 1:100, respectively. Fluorescent signals were captured with confocal microscopy and processed with Adobe Photoshop.…”

“…MARCM permits unique labeling of specific cells based on lineage and timing of birth as well as manipulation of gene function specifically in the uniquely labeled cells within otherwise wild-type organisms Lee and Luo, 2001). This control is particularly critical in the case of Kr-h1, since Drosophila Kr-h1 mutants die either around larval hatching or during metamorphosis (Pecasse et al, 2000;Beck et al, 2004), making it impossible to assess the function of Kr-h1 through formation of the adult neural circuitry in these strains. Finally, we assessed the interaction of neuronal expression of Kr-h1 with ecdysone transcriptional networks (Truman et al, 1994;Lee et al, 2000) and TGF-b regulation of axon growth (Zheng et al, 2003(Zheng et al, , 2006, another major mediator of neural patterning.…”

Orthodenticle and Kruppel homolog 1 regulate Drosophila photoreceptor maturation

“…As expected, we also noted a 74-fold decrease in the levels of otd transcripts in otd UVI versus WT retinas. Interestingly, among the genes whose transcription is differentially regulated in otd retinas, we found known targets of 20E signaling: fushi tarazu transcription factor 1 (ftz-f1), Ecdysone-induced protein 78C (Eip78C), and a modulator of this signaling pathway, Kr-h1 (12)(13)(14)(15)(16)(17). This observation suggests that, in concert with Otd, the systemic hormone 20E might be important to regulate PR maturation.…”

“…Previous work in the hemimetabolous insects, thrips, Thysanoptera, and in the beetle Tribolium castaneum, suggest that Kr-h1 could be involved in mediating antimetamorphic signals (21,22). In addition, studies in Drosophila show that Kr-h1 orchestrates 20E-regulated transcriptional pathways during embryogenesis and metamorphosis (15,16). It is therefore tempting to speculate that Kr-h1 could play an important role transducing systemic hormone signaling at the cellular level.…”