Differential gene expression during early development in recently evolved and sympatric Arctic charr morphs

Area of Science:

• Evolutionary Developmental Biology
• Genomics
• Speciation Research

Background:

• Phenotypic variation in closely related species can stem from genetic or environmental factors, altering gene transcription during development.
• Arctic charr (Salvelinus alpinus) exhibit significant phenotypic and resource polymorphism, particularly in Lake Thingvallavatn with four distinct morphs.
• Understanding the molecular basis of this variation is crucial for elucidating evolutionary divergence and speciation mechanisms.

Purpose of the Study:

• To investigate the molecular and developmental origins of polymorphism in Arctic charr.
• To compare gene expression patterns among different Arctic charr morphs during early embryonic development.
• To identify genetic factors contributing to phenotypic differences in sympatric populations.

Main Methods:

• RNA-sequencing and de novo transcriptome assembly were performed on embryos from three Arctic charr morphs.
• Gene expression was compared across morphs during a key developmental window preceding trophic structure formation.
• Quantitative PCR (qPCR) was used to validate differential gene expression findings.

Main Results:

• Developmental time was the primary factor influencing gene expression; RNA degradation (3'-bias) was a secondary factor.
• Arctic charr morph significantly affected the expression of numerous transcripts, with benthic morphs showing similar expression profiles.
• While specific genes like arid4a and tsn showed differential expression, broad functional enrichment analysis did not yield clear group distinctions.

Conclusions:

• Genetic divergence contributes to differential gene expression during early development in sympatric Arctic charr morphs.
• The findings support a model where altered gene expression underlies the evolution of distinct phenotypes and potentially speciation.
• Further research into specific regulatory genes and pathways is warranted to fully understand the molecular basis of Arctic charr polymorphism.