Origin and Evolution of Plant Long Terminal Repeat Retrotransposons with Additional Ribonuclease H

Area of Science:

• Genetics
• Evolutionary Biology
• Molecular Biology

Background:

• Retroviruses evolved from long terminal repeat retrotransposons (LTR-RTs) via structural changes, including acquiring an additional ribonuclease H (aRH) domain.
• Previous studies suggested independent evolution of this retrovirus-like structure in flowering plant Tat LTR-RTs, originating from rearrangements of ancestral Tat structures.

Purpose of the Study:

• To investigate the evolutionary history of the aRH domain acquisition in Tat LTR-RTs across a broader range of plant phyla.
• To test the hypothesis of Tat's aRH acquisition originating from sequential rearrangements of ancestral Tat structures.

Main Methods:

• Comparative genomics analysis of Tat LTR-RTs across extant plant phyla.
• Phylogenetic analysis to trace the evolutionary history of aRH domain acquisition.

Main Results:

• The retrovirus-like structure, characterized by the aRH domain, was found to have evolved in an ancestor of all land plants.
• This structure is present in diverse plant lineages, including clubmosses, hornworts, ferns, and gymnosperms.
• The findings indicate an ancient origin and broad propagation of this retrovirus-like structure in LTR-RTs.

Conclusions:

• The acquisition of the aRH domain by Tat LTR-RTs occurred early in land plant evolution.
• The widespread presence of this retrovirus-like structure suggests a significant, albeit not fully understood, adaptive advantage for LTR-RTs.