Horizontal gene transfer

Definition

The movement of genetic material between organisms through mechanisms other than parent-to-offspring (vertical) inheritance, including transformation, transduction, and conjugation. In arthropods, HGT occurs primarily between endosymbionts (such as Wolbachia or Rickettsia) and host nuclear genomes, as well as from dietary sources or viral integrations. This process contributes to genome innovation, metabolic pathway acquisition, and adaptive evolution across the tree of life.

Etymology

From Latin horizontem (boundary, limit) and English gene + transfer; 'horizontal' contrasts with 'vertical' (generational) inheritance patterns.

Example

The coffee berry borer (Hypothenemus hampeii) acquired a mannanase gene from bacteria via horizontal gene transfer, enabling it to digest galactomannan in coffee beans—an adaptation not present in closely related beetles.

Synonyms

• lateral gene transfer
• LGT

Related Terms

• endosymbiont
• Wolbachia
• Transposable element
• genome evolution
• Vertical transmission
• Parasitoid
• symbiogenesis

Usage Notes

Distinguished from vertical transmission by its non-generational, often cross-species nature. In insects and arachnids, HGT detection requires careful phylogenetic analysis to distinguish true transfer from contamination or ancestral retention. The term is sometimes restricted to prokaryotes in older literature, but eukaryotic HGT is now well-documented, particularly in taxa with intimate microbial associations.