The making of a queen: TOR pathway is a key player in diphenic caste development.
BACKGROUND
Honey bees (Apis mellifera) provide a principal example of diphenic development. Excess feeding of female larvae results in queens (large reproductives). Moderate diet yields workers (small helpers). The signaling pathway that links provisioning to female developmental fate is not understood, yet we reasoned that it could include TOR (target of rapamycin), a nutrient- and energy-sensing kinase that controls organismal growth.


RESULTS
Here, the role of Apis mellifera TOR (amTOR) in caste determination is examined by rapamycin/FK506 pharmacology and RNA interference (RNAi) gene knockdown. We show that in queen-destined larvae, the TOR inhibitor rapamycin induces the development of worker characters that are blocked by the antagonist FK506. Further, queen fate is associated with elevated activity of the Apis mellifera TOR encoding gene, amTOR, and amTOR gene knockdown blocks queen fate and results in individuals with worker morphology.


CONCLUSIONS
A much-studied insect dimorphism, thereby, can be governed by the TOR pathway. Our results present the first evidence for a role of TOR in diphenic development, and suggest that adoption of this ancestral nutrient-sensing cascade is one evolutionary pathway for morphological caste differentiation in social insects.
Patel
Avani
A
School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.
Fondrk
M Kim
MK
Kaftanoglu
Osman
O
Emore
Christine
C
Hunt
Greg
G
Frederick
Katy
K
Amdam
Gro V
GV
D000818:Animals; D001516:Bees / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006608:Hierarchy, Social; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases
D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus