Two Tor genes in the silkworm Bombyx mori

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• Target of rapamycin (TOR) is a key regulator of cellular and organismal growth, metabolism, development, and survival.
• TOR proteins are part of the phosphatidylinositol 3-kinase-related kinase family.
• Understanding TOR function is crucial for comprehending fundamental biological processes.

Purpose of the Study:

• To identify and characterize paralogous Tor genes in the silkworm Bombyx mori.
• To investigate the evolutionary and structural conservation of these genes.
• To analyze the expression patterns and regulation of BmTor1 and BmTor2 during development and in response to environmental cues.

Main Methods:

• Bioinformatic analysis of silkworm genome to identify Tor gene copies.
• Nucleotide and amino acid sequence analysis for evolutionary and structural comparison.
• Gene expression analysis across different tissues and developmental stages.
• Quantitative analysis of gene expression changes in response to starvation and 20-hydroxyecdysone (20E).

Main Results:

• Two paralogous Tor genes, BmTor1 and BmTor2, were identified in Bombyx mori, originating from an inverted repeat.
• BmTor1 is likely the orthologue, while BmTor2 is a duplicate, with both genes showing evolutionary and structural conservation.
• Both BmTor genes exhibit similar tissue distribution, with highest expression in the nervous system.
• Maximal expression levels were observed during the 4th larval-molting and larval-pupal transition stages.
• Starvation and 20E treatment up-regulated both BmTor genes, with BmTor2 showing higher sensitivity.

Conclusions:

• This study reports the first identification of two Tor gene copies in a higher eukaryote.
• The BmTor genes are significantly involved in larval molting and the larval-pupal transition.
• Their induction by starvation and 20E highlights their role in developmental regulation and stress response in silkworms.