Decapentaplegic signaling regulates Wingless ligand production and target activation during Drosophila wing development

Phenotypical and genetical characterization of the Mad1-2 allele during Drosophila wing development

Growth and patterning of Drosophila wing depends upon the sequential organizing activities of Hedgehog (Hh) and Decapentaplegic (Dpp) signaling pathways. The Hh signaling directly activates the expression of dpp through the transcription factor cubitus interruptus (Ci). Dpp itself functions as a long-range morphogen to promote cell proliferation and differentiation through an essential transcription factor encoded by Mad. Here we report that the Mad^1-2 allele exhibits phenotypes distinct from classical Dpp pathway mutants in the developing wing. The activity of Dpp signaling is attenuated in Mad^1-2 mutant cells. However, activation of Dpp signaling is found in a subset of cells surrounding homozygous Mad^1-2 clones when the clones are located at the anterior compartment of wing disc. Further analysis reveals that Mad^1-2 mutant cells display high level of Hh signaling activity and accumulate significant amount of Ci. Unexpectedly, whole genome resequencing identifies multiple mutations in the 3'UTR region of Pka-C1 genomic loci in the Mad^1-2 stock. We provide genetic and molecular evidence that the Pka-C1 mutations carried by Mad^1-2 likely underlies the observed Hh signaling defects. Therefore, the contribution of Pka-C1 mutation should be taken in consideration when analyzing Mad^1-2 phenotypes. The isolation of independent Mad and Pka-C1 alleles from the Mad^1-2 stock further supports our conclusions.

Hedgehog signaling regulates regenerative patterning and growth in Harmonia axyridis leg

Appendage regeneration has been widely studied in many species. Compared to other animal models, Harmonia axyridis has the advantage of a short life cycle, is easily reared, has strong regeneration capacity and contains systemic RNAi, making it a model organism for research on appendage regeneration. Here, we performed transcriptome analysis, followed by gene functional assays to reveal the molecular mechanism of H. axyridis leg regenerative growth process. Signaling pathways including Decapentaplegic (Dpp), Wingless (Wg), Ds/Ft/Hippo, Notch, Egfr, and Hedgehog (Hh) were all upregulated during the leg regenerative patterning and growth. Among these, Hh and its auxiliary receptor Lrp2 were required for the proper patterning and growth of the regenerative leg. The targets of canonical Hh signaling were required for the regenerative growth which contributes to the leg length, but were not essential for the pattern formation of the regenerative leg. dpp, wg and leg developmental-related genes including rn, dac and Dll were all regulated by hh and lrp2 and may play an essential role in the regenerative patterning of the leg.