Horizontal Gene Transfer in Fungi

Abstract

Horizontal gene transfer (HGT), the sharing of genes between species outside of inheritance, is a common feature among prokaryotes, but a growing body of evidence supports HGT in eukaryotic genomes. The driving forces behind horizontal gene transfer occur within a shared environment and are selective—meaning they improve survivability of stress, increase nutrient access, or provide an evolutionary advantage. The development of toxic and pathogenic properties was one of the first indications of phenotypic transfer among fungal species. A growing species diversity of genome sequences has brought a new set of tools to tracking HGT. The detection of HGT based on sequence similarity utilizes species tree phylogenies, which compare similarity of core-conserved genes to determine lineage. Divergence of an HGT candidate gene from a phylogenetic background tree can show interspecies DNA transfer. It is by following phenotypes and analysis of DNA sequence context and content that we can uncover previous transfer events and track lab-fostered and recorded HGT. Evidence of HGT is found heavily in parasitic and pathogenic fungi; both of these lifestyles rely on phagocytosis and assimilation of host parts and pieces, suggesting phagocytosis is implicated in DNA uptake mechanisms. Our understanding of the molecular mechanisms of DNA uptake and incorporation of foreign DNA into fungal genomes, i.e., natural competence, remains based on a set of laboratory conditions used in molecular transformation. The mechanism of DNA uptake in the natural world and new DNA incorporation remain under investigation.