An analysis of the phylogenetic distribution of the pea pathogenicity genes of Nectria haematococca MPVI supports the hypothesis of their origin by horizontal transfer and uncovers a potentially new pathogen of garden pea: Neocosmospora boniensis

Abstract

The filamentous fungus Nectria haematococca mating population VI (MPVI) contains a cluster of genes required to cause disease on pea. This cluster of pea pathogenicity genes (the PEP cluster) is located on a supernumerary chromosome that is dispensable for normal growth in culture. The genes in the PEP cluster have a different G+C content and codon usage compared with the genes located on the other chromosomes and a non-homogeneous distribution within the species. These features suggest that the PEP cluster may have been acquired by N. haematococca MPVI through horizontal gene transfer (HGT). In this work, we show that homologues of the PEP genes are present in another pea pathogen, Fusarium oxysporum f. sp. pisi, but are not common among fungi that are phylogenetically closely related to N. haematococca MPVI. This phylogenetic discontinuity supports the hypothesis that the PEP cluster originated by HGT. Our analysis has also determined that homologues for all the PEP genes are present in Neocosmospora boniensis. A molecular characterization of the PEP homologues in this fungus shows that they are organized as a cluster, which has a different physical organization from the PEP cluster in N. haematococca. In addition, although no reports have been found to show that N. boniensis is a naturally occurring pea pathogen, we show here that this species is able to cause disease on pea.

Evolution of Patchily Distributed Proteins Shared between Eukaryotes and Prokaryotes: Dictyostelium as a Case Study

“…Gene exchanges may indeed lead to direct changes of the phenotype of the recipient [Andersson, 2009a]. For example, transfer of virulence factors between different lineages of fungi has led to emergences of new plant pathogens within historical time [Friesen et al, 2006;Temporini and VanEtten, 2004]. The results presented in this study indicate that gene exchange occurs between soil organisms from all domains.…”

Lateral gene transfer in eukaryotes

“…Nevertheless, gene transfer events are not totally absent from the genome evolution of fungi; the yeast flavohemoglobin has been identified to have bacterial origin [77], and most enzymes that play important roles in the degradation of cellulose in rumen fungi have been shown to have been acquired via LGT from rumen bacteria, indicating that the process of gene transfer was probably the key event for the colonization of the rumen by fungi [86]. Additionally, discontinuous phylogenetic distribution of pea pathogenicity gene clusters in two filamentous fungi suggests that transfer of genes could, at least occasionally, be involved in the evolution of fungal pathogenicity [87].…”

Current status of the taxonomic position of Fusarium oxysporum formae specialis cubense within the Fusarium oxysporum complex

“…Multi-gene phylogenies not only revealed the polyphyletic nature of Foc but also that pathogenicity towards a specific cultivar evolved convergently (Baayen et al, 2000;Fourie et al, 2009;O'Donnell et al, 2009;O'Donnell et al, 1998). This is, however, not unexpected since this informal taxonomic ranking is based on pathogenicity towards a specific host plant (Kistler, 2000), and thus generally subject to strong selection pressure and possibly horizontal gene transfer events (Nimchuk et al, 2003;Temporini and VanEtten, 2004;Van der Does and Rep, 2007;Yoon et al, 2007). Recently, comparative genomics of F. graminearum, F. verticillioides and F. oxysporum f.sp.…”