Recurrent evolution of heat-responsiveness in Brassicaceae COPIA elements

Area of Science:

• Genomics
• Molecular Biology
• Evolutionary Biology

Background:

• Host genome defense mechanisms suppress transposable element (TE) mobilization.
• Arabidopsis thaliana COPIA78/ONSEN retrotransposons possess heat-responsive elements (HREs) in their cis-regulatory regions, activating TEs under heat stress.
• The evolutionary conservation and prevalence of this heat-responsiveness trait across species remain largely unexplored.

Purpose of the Study:

• To investigate the commonality and evolutionary history of heat-responsive transposable elements (TEs) in Brassicaceae.
• To identify the major families of heat-responsive TEs in Arabidopsis lyrata and Arabidopsis thaliana.
• To determine the role of heat shock factor binding elements (HREs) in TE heat-responsiveness and evolution.

Main Methods:

• Comparative genomics analysis of TE families across seven Brassicaceae species.
• Identification and characterization of heat-responsive elements (HREs) within the long terminal repeats (LTRs) of TEs.
• Phylogenetic analysis to trace the evolutionary history of HREs, including ONSEN.

Main Results:

• ONSEN, COPIA37, TERESTRA, and ROMANIAT5 were identified as major heat-responsive TEs in A. lyrata and A. thaliana.
• Heat-responsiveness in COPIA families correlates with the presence of high-affinity heat shock factor binding HREs in seven Brassicaceae species.
• The ONSEN HRE is ancient and conserved, evolving via proto-HRE duplication, while most other HREs are species-specific; ONSEN HRE in Boechera stricta lost heat-responsiveness due to mutations.

Conclusions:

• Heat-responsive elements (HREs) are a conserved, yet often species-specific, feature in Brassicaceae transposable elements (TEs).
• The evolution of HREs, particularly the conserved ONSEN HRE, highlights the dynamic co-evolutionary relationship between hosts and TEs.
• Acquisition of HREs may not confer an immediate selective advantage but can enhance the long-term survival probability of TEs within host genomes.