mTOR Complex 1 Implicated in Aphid/Buchnera Host/Symbiont Integration

Area of Science:

• Molecular Biology
• Symbiosis Research
• Insect Physiology

Background:

• Obligate nutritional endosymbioses represent intimate host-bacterial associations.
• Understanding host-endosymbiont integration is crucial for insect biology.
• The mechanistic target of rapamycin (mTOR) pathway integrates nutrition with cellular processes.

Purpose of the Study:

• To annotate and characterize the mTOR pathway in aphids.
• To investigate the role of mTOR in integrating aphid hosts with their bacterial endosymbionts, Buchnera aphidicola.
• To explore the functional significance of mTOR signaling in aphid-bacterial symbiosis.

Main Methods:

• BLASTp searches and Hidden Markov Models for mTOR gene annotation in two aphid species.
• RNA sequencing to construct reference transcriptomes for bacteriocyte, gut, and whole insect tissues.
• Differential gene expression analysis to compare mTOR pathway activity in different tissues.

Main Results:

• All known invertebrate mTOR pathway genes were identified in aphids, with some duplications.
• Genes of the amino acid-sensitive mTOR Complex 1 showed higher expression in bacteriocytes compared to mTOR Complex 2.
• Key amino acid-sensing mTOR genes were upregulated in bacteriocytes, with a specific transporter (SLC38A9 ortholog) showing significantly higher expression.

Conclusions:

• The mTOR pathway is likely functionally significant in mediating the integration of Buchnera aphidicola within aphid hosts.
• Differential expression of mTOR pathway components suggests a role in nutrient sensing and resource allocation within bacteriocytes.
• This study provides novel insights into the molecular mechanisms underlying aphid nutritional endosymbiosis.