Panel A: A diagram of the canonical Torso signaling pathway, illustrating the sequence from Torso to the transcription of somatic terminal signaling factors. Key components include Torso, Trunk, Csw, Shc, Sos, Ras, Raf, Ksr, Dsor1, and Rolled. The diagram shows the flow from Torso activation to the transcription process. Panel B: A heatmap showing the percentage of embryos with phenotypes related to PGC formation and lethality when various components of the Torso signaling pathway are knocked down using RNAi. The components include torso, shc, sos, ras, csw, raf, ksr, dsor1, and rolled. The heatmap uses a color gradient to indicate the percentage of embryos with each phenotype. Panel C: Immunostained images of embryos showing Vasa, dpERK, and DAPI staining. Each row represents a different maternal genotype with images showing Vasa in green, dpERK in magenta, and DNA in blue. The images are labeled with the specific component knocked down.
Ras is the most downstream component in the canonical Torso signaling pathway that can antagonize PGC formation. (A) Diagram of the canonical Torso signaling pathway, which is required to upregulate transcription of somatic patterning genes in the embryo. *Note that these results place Csw downstream of Ras, consistent with findings by Allard et al. (1996). (B) The canonical Torso signaling pathway components were knocked down in gcl−/− mothers, using RNAi driven with the germline-specific driver matTubGal4 during oogenesis. The percentage of embryos from these mutant mothers with Vasa-positive PGCs was calculated and plotted as a score for PGC formation. Lethality in these embryos was also scored. The ubiquitous driver TubGAL4 was used to assess knockdown efficiency. n > 100 embryos were scored for each condition. (C) Representative embryo of indicated maternal genotypes, nuclear cycle 13–14. Fixed embryos were immunostained with anti-Vasa (green) to count PGCs and anti-dpERK (magenta) to assess knock-down efficiency. DNA (blue). Scale bar = 50 μm.