Adaptation for horizontal transfer in a homing endonuclease

Area of Science:

• Molecular Biology
• Evolutionary Genetics
• Microbial Ecology

Background:

• Selfish genetic elements, such as homing endonuclease genes (HEGs), can degenerate if fixed within a population.
• Horizontal gene transfer (HGT) is a proposed mechanism for the long-term persistence of such genes.
• The VDE gene, a nuclear HEG found in yeast, serves as a model to study HGT dynamics.

Purpose of the Study:

• To investigate the evolutionary history and transmission patterns of the VDE gene across yeast species.
• To determine if VDE exhibits adaptations favoring horizontal transfer.
• To understand the role of HGT in the persistence and distribution of selfish genetic elements.

Main Methods:

• Phylogenetic analysis of the VDE gene across 24 yeast species.
• Comparative sequence analysis focusing on conserved regions, particularly the HEG recognition site and critical homing sites.
• Assessment of gene conservation patterns in relation to transmission mechanisms.

Main Results:

• Phylogenetic analyses indicate that horizontal transmission has been a frequent event in the evolutionary history of VDE.
• The VDE gene and its recognition sequence show unusually high conservation, especially at critical homing sites.
• These conservation patterns suggest VDE is specifically adapted for efficient horizontal transmission.

Conclusions:

• Horizontal gene transfer is a crucial factor for the long-term survival of selfish genes like VDE, preventing their degeneration.
• Adaptations within VDE facilitate its horizontal transmission, driven by selection pressures at genomic and variant levels.
• The frequency of HGT is a significant determinant of VDE's distribution and abundance in yeast populations.