Other studies have shown that ecological proximity may be linked to HGT. For example, a yeast wine strain (S. cerevisiae EC118) has gained 65 KB of genetic material from Zygosaccharomyces bailii (a major contaminant of wine fermentations; Novo et al., 2009). The genome of Mycosphaerella graminicola also displays evidence of whole chromosomal transfer (Goodwin et al., 2011). M. graminicola contains 21 chromosomes; eight of these are dispensable and originated from an unknown fungal source, which is most likely the result of a somatic fusion with another species that had eight or more chromosomes (Goodwin et al., 2011). Another process linked to HGT in fungal species is anastomosis. Filamentous fungi frequently fuse conidia and conidial germlings using a specialized hypha known as conidial anastomosis tubes; these allow interconnected germlings to act as a single coordinated individual (regulating Selumetinib research buy water, nutrients, signal molecules, nuclei and organelles; Read
et al., 2009) and also allow for genetic exchange (Roca et al., 2004). Although non-self-recognition systems have evolved in fungi (Glass & Kaneko, 2003), there is evidence to suggest Akt inhibitor that interspecies anastomosis between fungal pathogens may have occurred (Friesen et al., 2006; Xie et al., 2008). As well as mechanisms that facilitate fungal HGT, there are also potential barriers that may oppose it. For example, fungal nuclei are membrane bound, and also differential intron processing and incompatible gene promoters may need to be overcome (Keeling & Palmer, 2008). Furthermore, fungal genetic material is stored in chromatin; while gene-silencing mechanisms such as repeat induced point mutation and methylation induced premeiotically systems have the potential to pseudogenize foreign genes with repetitive elements. The process Alanine-glyoxylate transaminase of meiotic silencing by unpaired DNA (Shiu et al., 2001) is yet another possible barrier to HGT; indeed, it has been proposed that (meiotic) sex has evolved in eukaryotes as a mechanism to
check the identity and limit the impact of foreign DNA (Glansdorff et al., 2009). Another possible barrier to HGT is an alternative genetic code. The human pathogen Candida albicans and close relatives translate the codon CTG as serine instead of leucine. Recent analyses of species from the CTG clade (Fitzpatrick et al., 2006) could only locate four incidences of bacterial to fungal HGT since the CTG codon reassignment approximately 170 million years ago (Fitzpatrick et al., 2008; Marcet-Houben & Gabaldon, 2010). Such low incidences of HGT over such a long time period support the hypothesis that genetic code alterations act as barriers to HGT. Comparative fungal genomic analyses have shown the importance that HGT plays in the evolution of fungi. For example, Hall and Dietrich have shown that S.