TORC1 regulators Iml1/GATOR1 and GATOR2 control meiotic entry and oocyte development in Drosophila

Proc Natl Acad Sci U S A. 2014 Dec 30;111(52):E5670-7. doi: 10.1073/pnas.1419156112. Epub 2014 Dec 15.

Abstract

In single-cell eukaryotes the pathways that monitor nutrient availability are central to initiating the meiotic program and gametogenesis. In Saccharomyces cerevisiae an essential step in the transition to the meiotic cycle is the down-regulation of the nutrient-sensitive target of rapamycin complex 1 (TORC1) by the increased minichromosome loss 1/ GTPase-activating proteins toward Rags 1 (Iml1/GATOR1) complex in response to amino acid starvation. How metabolic inputs influence early meiotic progression and gametogenesis remains poorly understood in metazoans. Here we define opposing functions for the TORC1 regulatory complexes Iml1/GATOR1 and GATOR2 during Drosophila oogenesis. We demonstrate that, as is observed in yeast, the Iml1/GATOR1 complex inhibits TORC1 activity to slow cellular metabolism and drive the mitotic/meiotic transition in developing ovarian cysts. In iml1 germline depletions, ovarian cysts undergo an extra mitotic division before meiotic entry. The TORC1 inhibitor rapamycin can suppress this extra mitotic division. Thus, high TORC1 activity delays the mitotic/meiotic transition. Conversely, mutations in Tor, which encodes the catalytic subunit of the TORC1 complex, result in premature meiotic entry. Later in oogenesis, the GATOR2 components Mio and Seh1 are required to oppose Iml1/GATOR1 activity to prevent the constitutive inhibition of TORC1 and a block to oocyte growth and development. To our knowledge, these studies represent the first examination of the regulatory relationship between the Iml1/GATOR1 and GATOR2 complexes within the context of a multicellular organism. Our data imply that the central role of the Iml1/GATOR1 complex in the regulation of TORC1 activity in the early meiotic cycle has been conserved from single cell to multicellular organisms.

Keywords: Drosophila; GATOR1; GATOR2; Iml1; meiosis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology
  • Cell Cycle Proteins
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster
  • Female
  • Meiosis / drug effects
  • Meiosis / physiology*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Oocytes / cytology
  • Oocytes / metabolism*
  • Oogenesis / drug effects
  • Oogenesis / physiology*
  • Sirolimus / pharmacology
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*

Substances

  • Anti-Bacterial Agents
  • Cell Cycle Proteins
  • Drosophila Proteins
  • Nuclear Proteins
  • TORC1 protein complex, Drosophila
  • Transcription Factors
  • mio protein, Drosophila
  • Sirolimus