The nuclear receptor E75A has a novel pair-rule-like function in patterning the milkweed bug, Oncopeltus fasciatus

Department of Biology, University of Washington, Seattle, WA 98195-1800, USA.
Developmental Biology (Impact Factor: 3.55). 08/2009; 334(1):300-10. DOI: 10.1016/j.ydbio.2009.06.038
Source: PubMed


Genetic studies of the fruit fly Drosophila have revealed a hierarchy of segmentation genes (maternal, gap, pair-rule and HOX) that subdivide the syncytial blastoderm into sequentially finer-scale coordinates. Within this hierarchy, the pair-rule genes translate gradients of information into periodic stripes of expression. How pair-rule genes function during the progressive mode of segmentation seen in short and intermediate-germ insects is an ongoing question. Here we report that the nuclear receptor Of'E75A is expressed with double segment periodicity in the head and thorax. In the abdomen, Of'E75A is expressed in a unique pattern during posterior elongation, and briefly resembles a sequence that is typical of pair-rule genes. Depletion of Of'E75A mRNA caused loss of a subset of odd-numbered parasegments, as well as parasegment 6. Because these parasegments straddle segment boundaries, we observe fusions between adjacent segments. Finally, expression of Of'E75A in the blastoderm requires even-skipped, which is a gap gene in Oncopeltus. These data show that the function of Of'E75A during embryogenesis shares many properties with canonical pair-rule genes in other insects. They further suggest that parasegment specification may occur through irregular and episodic pair-rule-like activity.

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Available from: Lynn M Riddiford
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    • "Examination of PRG expression and function in insects other than Drosophila revealed that this level of the segmentation gene cascade is, to some degree, conserved in insects (e.g. [19-21]). The expression profile of PRGs in most insects is, however, somewhat different from that in Drosophila. "
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    • "In particular, we identified many of the ecdysone-regulated genes that play key roles during molting and metamorphosis, including E75, HR3, and HR4 (Table 4). The presence of these genes in the ovaries and early embryos of O. fasciatus corroborates recent studies that implicate ecdysone-response genes in key developmental processes during embryogenesis [59-61]. As might be expected for a situation where ecdysone regulates embryonic development but not molting, transcripts encoding insect peptide hormones implicated in eclosion behavior, such as ecdysis-triggering hormone, eclosion hormone and crustacean cardioactive peptide, were not detected. "
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