Host-induced aneuploidy and phenotypic diversification in the Sudden Oak Death pathogen Phytophthora ramorum. (December 2016)

• Record Type: Journal Article
• Authors: Kasuga, Takao; Bui, Mai; Bernhardt, Elizabeth; Swiecki, Tedmund; Aram, Kamyar; Cano, Liliana; Webber, Joan; Brasier, Clive; Press, Caroline; Grünwald, Niklaus; Rizzo, David; Garbelotto, Matteo
• Is Part Of: BMC genomics. Volume 17:Number 1(2016)
• Page Start: 1
• Page End: 17
• Publication Date: 2016-12
• Subjects: Invasive pathogens -- Aneuploidy -- Transposable elements -- Loss of heterozygosity; Genomes -- Periodicals; Gene mapping -- Periodicals; Genomics -- Periodicals; Base Sequence -- Periodicals; Chromosome Mapping -- Periodicals; Genetic Techniques -- Periodicals; Sequence Analysis, DNA -- Periodicals; 572.8605
• DOI: 10.1186/s12864-016-2717-z
• Languages: English
• ISSNs: 1471-2164

Abstract

Abstract Background Aneuploidy can result in significant phenotypic changes, which can sometimes be selectively advantageous. For example, aneuploidy confers resistance to antifungal drugs in human pathogenic fungi. Aneuploidy has also been observed in invasive fungal and oomycete plant pathogens in the field. Environments conducive to the generation of aneuploids, the underlying genetic mechanisms, and the contribution of aneuploidy to invasiveness are underexplored. We studied phenotypic diversification and associated genome changes inPhytophthora ramorum, a highly destructive oomycete pathogen with a wide host-range that causes Sudden Oak Death in western North America and Sudden Larch Death in the UK. Introduced populations of the pathogen are exclusively clonal. In California, oak (Quercus spp. ) isolates obtained from trunk cankers frequently exhibit host-dependent, atypical phenotypes called non-wild type (nwt ), apparently without any host-associated population differentiation. Based on a large survey of genotypes from different hosts, we previously hypothesized that the environment in oak cankers may be responsible for the observed phenotypic diversification inP. ramorum . Results We show that both normal wild type (wt ) andnwt phenotypes were obtained whenwt P. ramorum isolates from the foliar hostCalifornia bay (Umbellularia californica ) were re-isolated from cankers of artificially-inoculated canyon live oak (Q. chrysolepis ). We also found comparablenwt phenotypes inP. ramorum isolates from a bark canker of Lawson cypress (Chamaecyparis lawsoniana ) in the UK; previouslynwt was not known to occur in this pathogen population. High-throughput sequencing-based analyses identified major genomic alterations including partial aneuploidy and copy-neutral loss of heterozygosity predominantly innwt isolates. Chromosomal breakpoints were located at or near transposons. Conclusion This work demonstrates that major genome alterations of a pathogen can be induced by its host species. This is an undocumented type of plant-microbe interaction, and its contribution to pathogen evolution is yet to be investigated, but one of the potential collateral effects ofnwt phenotypes may be host survival.