Torso receptor tyrosine kinase signaling in Drosophila melanogaster

Torso is a receptor tyrosine kinase that is uniformly distributed in the early embryo membrane but activated only at the anterior and posterior poles, where it specifies the terminal structures. Local activation depends on Torso-like, which is deposited at the poles by follicle cells and acts together with eggshell components (Nasrat/fs(1)N, Polehole/fs(1)M3 and Closca) to allow activation of Torso by its ligand Trunk. Torso signals through Drk, Sos and Ras to the Raf-MEK (Dsor1)-ERK (Rolled) cascade. ERK phosphorylation relieves repression by Capicua, which with the corepressor Groucho represses the terminal gap genes tailless and huckebein outside the poles. In the larval prothoracic gland, Torso is activated by prothoracicotropic hormone (PTTH) to trigger ecdysone production and the onset of metamorphosis.

MODULE:dmel_torso_signalingDRAFTCONCRETESignaling Pathwaymodules/dmel_torso_signaling.yaml

torso signaling pathwayGO:0008293 terminal region determinationGO:0007362

FB:FBgg0000934

FlyBase gene group TORS: Torso signaling pathway

FlyBase release FB2026_03 groups 31 D. melanogaster genes as torso signaling pathway (TORS); this module models that group.

GO:0008293

torso signaling pathway

GO term grounding the module as torso signaling pathway.

GO:0007362

terminal region determination

GO term grounding the module as terminal region determination.

Boundary. The Ras-ERK components are shared with other receptor tyrosine kinase pathways. The connection from MAPK cascade to transcriptional output is negative because ERK inactivates the repressor Capicua; Bicoid sits in the same part only because FlyBase lists it among core components. Rap1 is a FlyBase core member; its role relative to Ras in Torso signaling is less clear. FlyBase groups realized by this module: TORS (FBgg0000934). Subgroups folded into it: TORS-C. FlyBase also curates regulator sets for this pathway, which are context and not modelled as parts: TORS-P (positive regulators of torso signaling pathway, 2 genes); TORS-N (negative regulators of torso signaling pathway, 7 genes). Participants were generated from the FlyBase gene-group membership and mapped to UniProtKB by projects/FLYBASE_GENE_GROUPS/generate_modules.py from module_specs/dmel_torso_signaling.yaml. Member genes with a gene review in this repository: drk, Dsor1, Raf, Ras85D, rl, Sos.

10Nodes

7Parts

1Variant Sets

2Variants

22Annotons

6Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:dmel_torso_signaling deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Function consistency and core coverage

5 gene-function check(s) reflected in core functions · 0 conflict(s) · 5 evidence or coverage gap(s) (10 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

Annoton	Participant	Function	Assessment
torso_receptor_tor	tor UniProtKB:P18475 Gene	transmembrane receptor protein tyrosine kinase activity GO:0004714	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
torso_adaptors_csw	csw UniProtKB:P29349 Gene	protein tyrosine phosphatase activity GO:0004725	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
ras_activation_sos	Sos UniProtKB:P26675 Gene	guanyl-nucleotide exchange factor activity GO:0005085	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
ras_activation_ras85d	Ras85D UniProtKB:P08646 Gene	GTPase activity GO:0003924	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
mapk_cascade_raf	Raf UniProtKB:P11346 Gene	MAP kinase kinase kinase activity GO:0004709	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
mapk_cascade_dsor1	Dsor1 UniProtKB:Q24324 Gene	MAP kinase kinase activity GO:0004708	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
mapk_cascade_rl	rl UniProtKB:P40417 Gene	MAP kinase activity GO:0004707	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
transcriptional_output_cic	cic UniProtKB:Q9U1H0 Gene	DNA-binding transcription repressor activity, RNA polymerase II-specific GO:0001227	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
transcriptional_output_gro	gro UniProtKB:P16371 Gene	transcription corepressor activity GO:0003714	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
transcriptional_output_bcd	bcd UniProtKB:P09081 Gene	DNA-binding transcription factor activity, RNA polymerase II-specific GO:0000981	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.

Feedback loops (advisory, prose-driven: a regulator counts as "feedback" when its own description says so)

✓ every negative regulator described as feedback has an upstream edge closing the loop.

mapk_cascade ⊣ transcriptional_output [closed]
mapk_cascade is regulated by ras_activation: feedback loop closed

Gene-review completeness (6/22 grounded genes reviewed)

2 complete review(s) · 5 with deep research · 16 missing review · 1 reviewed but lacking deep research

Gene	Review	Complete	Deep research
cnk A1ZAS2	✗	—	—
clos A8DQW8	✗	—	—
drk Q08012	✓	74/76	✓
Dsor1 Q24324	✓	✓	✓
fs(1)N O76904	✗	—	—
Rap1 P08645	✗	—	—
bcd P09081	✗	—	—
gro P16371	✗	—	—
tor P18475	✗	—	—
csw P29349	✗	—	—
tsl P40689	✗	—	—
trk Q24155	✗	—	—
ksr Q24171	✗	—	—
cic Q9U1H0	✗	—	—
Shc Q9V3C8	✗	—	—
dos Q9VZZ9	✗	—	—
fs(1)M3 Q9W451	✗	—	—
Raf P11346	✓	89/90	✓
Ras85D P08646	✓	✓	✓
rl P40417	✓	119/125	✓
Sos P26675	✓	47/50	✗
Ptth X2JCX9	✗	—	—

Tree

Torso signaling pathwaySignaling Pathwaydmel_torso_signaling

Parts
1. 1. localized activation at the embryo poles
2. Torso-like and eggshell factorsSignaling Pathwayterminal_eggshell_factors
  
  Annotons
  - tsl Torso-like and eggshell factors Gene Product: tsl
  - fs(1)N Torso-like and eggshell factors Gene Product: fs(1)N
  - fs(1)M3 Torso-like and eggshell factors Gene Product: fs(1)M3
  - clos Torso-like and eggshell factors Gene Product: clos
3. 2. ligands
4. Torso ligandsSignaling Pathwaytorso_ligands
  
  Variants
  1. Trunk or PTTH (One Or More)
    
    Trunk in the early embryoSignaling Pathwaytrunk_ligand
    
    Annotons
    
    trk Trunk in the early embryo Gene Product: trk
    
    PTTH in the prothoracic glandSignaling Pathwayptth_ligand
    
    Annotons
    
    Ptth PTTH in the prothoracic gland Gene Product: Ptth
5. 3. receptor
6. Torso receptor tyrosine kinaseSignaling Pathwaytorso_receptor
  
  Annotons
  - tor Torso receptor tyrosine kinase Gene Product: tor
7. 4. phosphotyrosine adaptors and docking proteins
8. Receptor-proximal adaptorsSignaling Pathwaytorso_adaptors
  
  Annotons
  - drk Receptor-proximal adaptors Gene Product: drk
  - dos Receptor-proximal adaptors Gene Product: dos
  - csw Receptor-proximal adaptors Gene Product: csw
  - Shc Receptor-proximal adaptors Gene Product: Shc
9. 5. small GTPase activation
10. Sos, Ras and Rap1Signaling Pathwayras_activation
  
  Annotons
  - Sos Sos, Ras and Rap1 Gene Product: Sos
  - Ras85D Sos, Ras and Rap1 Gene Product: Ras85D
  - Rap1 Sos, Ras and Rap1 Gene Product: Rap1
11. 6. MAPK cascade
12. Raf-MEK-ERK cascade with scaffoldsSignaling Pathwaymapk_cascade
  
  Annotons
  - Raf Raf-MEK-ERK cascade with scaffolds Gene Product: Raf
  - ksr Raf-MEK-ERK cascade with scaffolds Gene Product: ksr
  - cnk Raf-MEK-ERK cascade with scaffolds Gene Product: cnk
  - Dsor1 Raf-MEK-ERK cascade with scaffolds Gene Product: Dsor1
  - rl Raf-MEK-ERK cascade with scaffolds Gene Product: rl
13. 7. transcriptional output
14. Capicua-Groucho repression and BicoidSignaling Pathwaytranscriptional_output
  
  Annotons
  - cic Capicua-Groucho repression and Bicoid Gene Product: cic
  - gro Capicua-Groucho repression and Bicoid Gene Product: gro
  - bcd Capicua-Groucho repression and Bicoid Gene Product: bcd

Details

Context

Drosophila melanogasterNCBITaxon:7227

Torso signaling pathwaySignaling Pathwaydmel_torso_signaling

Receptor tyrosine kinase pathway in which Trunk (embryo) or PTTH (prothoracic gland) activate Torso and Ras-ERK, relieving Capicua repression.

torso signaling pathwayGO:0008293 terminal region determinationGO:0007362

Context

Drosophila melanogasterNCBITaxon:7227

Connections

terminal_eggshell_factors -> torso_ligands Positively Regulates

Torso-like and eggshell factors allow local production of active Trunk at the poles.

torso_ligands -> torso_receptor Positively Regulates

Trunk or PTTH activates Torso.

torso_receptor -> torso_adaptors Positively Regulates

The activated receptor recruits phosphotyrosine adaptors.

torso_adaptors -> ras_activation Positively Regulates

Drk recruits Sos, which activates Ras.

ras_activation -> mapk_cascade Positively Regulates

Ras-GTP activates Raf.

mapk_cascade -> transcriptional_output Negatively Regulates

ERK relieves Capicua-mediated repression of terminal genes.

Part 1: localized activation at the embryo poles

Torso-like and eggshell factorsSignaling Pathwayterminal_eggshell_factors

Torso-like is secreted by terminal follicle cells; Nasrat, Polehole and Closca are vitelline membrane-associated proteins required for terminal signaling.

Annotons

tsl Torso-like and eggshell factors

terminal_eggshell_factors_tsl

Participant: Gene Product: tsl

Gene Product:

tslUniProtKB:P40689

fs(1)N Torso-like and eggshell factors

terminal_eggshell_factors_fs_1_n

Participant: Gene Product: fs(1)N

Gene Product:

fs(1)NUniProtKB:O76904

fs(1)M3 Torso-like and eggshell factors

terminal_eggshell_factors_fs_1_m3

Participant: Gene Product: fs(1)M3

Gene Product:

fs(1)M3UniProtKB:Q9W451

clos Torso-like and eggshell factors

terminal_eggshell_factors_clos

Participant: Gene Product: clos

Gene Product:

closUniProtKB:A8DQW8

Part 2: ligands

Torso ligandsSignaling Pathwaytorso_ligands

Variant set: Trunk or PTTH (One Or More)

Trunk in the early embryoSignaling Pathwaytrunk_ligand

Annotons

trk Trunk in the early embryo

trunk_ligand_trk

Participant: Gene Product: trk

Gene Product:

trkUniProtKB:Q24155

PTTH in the prothoracic glandSignaling Pathwayptth_ligand

Annotons

Ptth PTTH in the prothoracic gland

ptth_ligand_ptth

Participant: Gene Product: Ptth

Gene Product:

PtthUniProtKB:X2JCX9

Part 3: receptor

Torso receptor tyrosine kinaseSignaling Pathwaytorso_receptor

Annotons

tor Torso receptor tyrosine kinase

torso_receptor_tor

Participant: Gene Product: tor

Gene Product:

torUniProtKB:P18475

Function

transmembrane receptor protein tyrosine kinase activityGO:0004714

Part 4: phosphotyrosine adaptors and docking proteins

Receptor-proximal adaptorsSignaling Pathwaytorso_adaptors

Annotons

drk Receptor-proximal adaptors

torso_adaptors_drk

Participant: Gene Product: drk

Gene Product:

drkUniProtKB:Q08012

dos Receptor-proximal adaptors

torso_adaptors_dos

Participant: Gene Product: dos

Gene Product:

dosUniProtKB:Q9VZZ9

csw Receptor-proximal adaptors

torso_adaptors_csw

Participant: Gene Product: csw

Gene Product:

cswUniProtKB:P29349

Function

protein tyrosine phosphatase activityGO:0004725

Shc Receptor-proximal adaptors

torso_adaptors_shc

Participant: Gene Product: Shc

Gene Product:

ShcUniProtKB:Q9V3C8

Part 5: small GTPase activation

Sos, Ras and Rap1Signaling Pathwayras_activation

Annotons

Sos Sos, Ras and Rap1

ras_activation_sos

Participant: Gene Product: Sos

Gene Product:

SosUniProtKB:P26675

Function

guanyl-nucleotide exchange factor activityGO:0005085

Ras85D Sos, Ras and Rap1

ras_activation_ras85d

Participant: Gene Product: Ras85D

Gene Product:

Ras85DUniProtKB:P08646

Function

GTPase activityGO:0003924

Rap1 Sos, Ras and Rap1

ras_activation_rap1

Participant: Gene Product: Rap1

Gene Product:

Rap1UniProtKB:P08645

Part 6: MAPK cascade

Raf-MEK-ERK cascade with scaffoldsSignaling Pathwaymapk_cascade

Annotons

Raf Raf-MEK-ERK cascade with scaffolds

mapk_cascade_raf

Participant: Gene Product: Raf

Gene Product:

RafUniProtKB:P11346

Function

MAP kinase kinase kinase activityGO:0004709

Processes

MAPK cascadeGO:0000165

ksr Raf-MEK-ERK cascade with scaffolds

mapk_cascade_ksr

Participant: Gene Product: ksr

Gene Product:

ksrUniProtKB:Q24171

Processes

MAPK cascadeGO:0000165

cnk Raf-MEK-ERK cascade with scaffolds

mapk_cascade_cnk

Participant: Gene Product: cnk

Gene Product:

cnkUniProtKB:A1ZAS2

Processes

MAPK cascadeGO:0000165

Dsor1 Raf-MEK-ERK cascade with scaffolds

mapk_cascade_dsor1

Participant: Gene Product: Dsor1

Gene Product:

Dsor1UniProtKB:Q24324

Function

MAP kinase kinase activityGO:0004708

Processes

MAPK cascadeGO:0000165

rl Raf-MEK-ERK cascade with scaffolds

mapk_cascade_rl

Participant: Gene Product: rl

Gene Product:

rlUniProtKB:P40417

Function

MAP kinase activityGO:0004707

Processes

MAPK cascadeGO:0000165

Part 7: transcriptional output

Capicua-Groucho repression and BicoidSignaling Pathwaytranscriptional_output

Capicua and Groucho repress terminal genes outside the poles; ERK signaling relieves this repression. Bicoid, the anterior morphogen, is a FlyBase core member because Torso signaling modulates its activity at the anterior pole.

Annotons

cic Capicua-Groucho repression and Bicoid

transcriptional_output_cic

Participant: Gene Product: cic

Gene Product:

cicUniProtKB:Q9U1H0

Function

DNA-binding transcription repressor activity, RNA polymerase II-specificGO:0001227

gro Capicua-Groucho repression and Bicoid

transcriptional_output_gro

Participant: Gene Product: gro

Gene Product:

groUniProtKB:P16371

Function

transcription corepressor activityGO:0003714

bcd Capicua-Groucho repression and Bicoid

transcriptional_output_bcd

Participant: Gene Product: bcd

Gene Product:

bcdUniProtKB:P09081

Function

DNA-binding transcription factor activity, RNA polymerase II-specificGO:0000981