The Potential for pathogenicity was present in the ancestor of the Ascomycete subphylum Pezizomycotina
1 CMPG, Department of Microbial and Molecular Systems, K.U. Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
2 Departments of Plant Systems Biology and Plant Biotechnology and Genetics, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium
3 Laboratory of Molecular Biology, Institute of Plant Biotechnology, Central University ‘Marta Abreu’ of Las Villas (UCLV), Santa Clara, Cuba
BMC Evolutionary Biology 2010, 10:318 doi:10.1186/1471-2148-10-318Published: 21 October 2010
Previous studies in Ascomycetes have shown that the function of gene families of which the size is considerably larger in extant pathogens than in non-pathogens could be related to pathogenicity traits. However, by only comparing gene inventories in extant species, no insights can be gained into the evolutionary process that gave rise to these larger family sizes in pathogens. Moreover, most studies which consider gene families in extant species only tend to explain observed differences in gene family sizes by gains rather than by losses, hereby largely underestimating the impact of gene loss during genome evolution.
In our study we used a selection of recently published genomes of Ascomycetes to analyze how gene family gains, duplications and losses have affected the origin of pathogenic traits. By analyzing the evolutionary history of gene families we found that most gene families with an enlarged size in pathogens were present in an ancestor common to both pathogens and non-pathogens. The majority of these families were selectively maintained in pathogenic lineages, but disappeared in non-pathogens. Non-pathogen-specific losses largely outnumbered pathogen-specific losses.
We conclude that most of the proteins for pathogenicity were already present in the ancestor of the Ascomycete lineages we used in our study. Species that did not develop pathogenicity seemed to have reduced their genetic complexity compared to their ancestors. We further show that expansion of gained or already existing families in a species-specific way is important to fine-tune the specificities of the pathogenic host-fungus interaction.