Widespread changes in gene expression accompany body size evolution in nematodes

Area of Science:

• Evolutionary biology
• Developmental biology
• Genomics

Background:

• Body size is a crucial trait influencing ecological and evolutionary patterns.
• Caenorhabditis inopinata, a nematode associated with figs, is significantly larger than its relatives, including Caenorhabditis elegans.
• Previous research indicated that C. inopinata's large size results from postembryonic cell expansion during development.

Purpose of the Study:

• To investigate the transcriptional basis of body size differences between C. inopinata and C. elegans.
• To compare gene expression patterns during the larval-to-adult transition in both species.

Main Methods:

• RNA sequencing (RNA-seq) was performed on C. elegans and C. inopinata across L3, L4, and adult developmental stages.
• A model comparison approach was used to identify orthologous genes with divergent expression dynamics between the two species.

Main Results:

• Most genes showed differential expression across developmental stages in both species.
• Genes related to neuronal function, behavior, stress response, developmental timing, and chromatin regulation exhibited divergent dynamics.
• Hypodermal collagens, genes involved in molting and body morphology, and transforming growth factor β signaling pathway genes displayed unique transcriptional patterns.

Conclusions:

• Widespread transcriptional divergence between C. inopinata and C. elegans may reflect their distinct ecological and morphological adaptations.
• Alternatively, this divergence could represent developmental system drift within the Caenorhabditis genus.
• This study provides a foundation for future functional genetic research into the evolution of body size.