Epichloë hybrida , sp. nov., an emerging model system for investigating fungal allopolyploidy.

Endophytes of the genusEpichloë(Clavicipitaceae, Ascomycota) frequently occur within cool-season grasses and form interactions with their hosts that range from mutualistic to antagonistic. ManyEpichloëspecies have arisen via interspecific hybridization, resulting in species with two or three subgenomes that retain all or nearly all of their original parental genomes, a process termed allopolyploidization. Here, we characterizeEpichloë hybrida, sp. nov., a mutualistic species that has increasingly become a model system for investigating allopolyploidy in fungi. TheEpichloëspecies so far identified as the closest known relatives of the two progenitors ofE. hybridaareE. festucaevar.loliiandE. typhina. We confirm that the nuclear genome ofE. hybridacontains two homeologs of most protein-coding genes fromE. festucaeandE. typhina, with genome-wide gene expression analysis indicating a slight bias in overall gene expression from theE. typhinasubgenome. Mitochondrial DNA is detectable only fromE. festucae, whereas ribosomal DNA is detectable only fromE. typhina. Inheriting ribosomal DNA from just one parent might be expected to preferentially favor interactions with ribosomal proteins from the same parent, but we find that ribosomal protein genes from both parental subgenomes are nearly all expressed equally inE. hybrida. Finally, we provide a comprehensive set of resources for this model system that are intended to facilitate further study of fungal hybridization by other researchers. [ABSTRACT FROM AUTHOR]