Sex allocation plasticity on a transcriptome scale: Socially sensitive gene expression in a simultaneous...

Area of Science:

• Evolutionary biology
• Molecular biology
• Reproductive biology

Background:

• Phenotypic plasticity enables organisms to optimize traits across environments.
• Sex allocation, a plastic life history trait in simultaneous hermaphrodites, involves balancing investment in male and female functions.
• Theory suggests increased male investment with group size due to sperm competition.

Purpose of the Study:

• To investigate sex allocation plasticity at the molecular level in the simultaneous hermaphrodite Macrostomum lignano.
• To determine if gene expression in M. lignano changes with social environment (group size).
• To link molecular changes to reproductive investment shifts.

Main Methods:

• Genome-wide RNA-Seq analysis of M. lignano across four group size treatments with 16 biological replicates.
• Whole-mount in situ hybridization to confirm transcript localization.
• RNA interference (RNAi) to test the function of candidate genes in gametogenesis.

Main Results:

• Over 10% of all transcripts and over 30% of gonad- and tail-specific transcripts showed differential expression based on group size.
• Transcriptional changes indicated a shift towards male reproductive investment with increasing group size and sperm competition.
• In situ hybridization confirmed organ-specific expression, and RNAi validated gene function in gametogenesis.

Conclusions:

• A significant proportion of sex-specific transcripts in M. lignano are plastic and environmentally responsive.
• These molecular changes are functionally relevant to reproductive phenotypes, supporting organismal-level predictions.
• The study bridges organismal and molecular approaches to understand sex allocation plasticity.