High-throughput genome sequencing of lichenizing fungi to assess gene loss in the ammonium transporter/ammonia permease gene family

BMC Genomics

Research Article

François Lutzoni¹  Tami R McDonald²  Olaf Mueller³  Fred S Dietrich³ 

[1] Department of Biology, Duke University, 27708, Durham, NC, USA;Department of Biology, Duke University, 27708, Durham, NC, USA;Department of Microbiology, University of Minnesota, 55455, Minneapolis, MN, USA;Department of Molecular Genetics and Microbiology, Duke University, 27710, Durham, NC, USA;

关键词: Ammonium transporter;    Ammonia permease;    Phylogeny;    Lichen symbiosis;    Fungi;    Genome;    Illumina;    Horizontal gene transfer;   

DOI  :  10.1186/1471-2164-14-225

 received in 2012-10-18, accepted in 2013-02-13,  发布年份 2013

来源: Springer

【 摘 要 】

BackgroundHorizontal gene transfer has shaped the evolution of the ammonium transporter/ammonia permease gene family. Horizontal transfers of ammonium transporter/ammonia permease genes into the fungi include one transfer from archaea to the filamentous ascomycetes associated with the adaptive radiation of the leotiomyceta. The horizontally transferred gene has subsequently been lost in most of the group but has been selectively retained in lichenizing fungi. However, some groups of lichens appear to have secondarily lost the archaeal ammonium transporter. Definitive assessment of gene loss can only be made via whole genome sequencing.ResultsAmmonium transporter/ammonia permease gene sequences were recovered from the assembled genomes of eight lichenizing fungi in key clades including the Caliciales, the Peltigerales, the Ostropomycetidae, the Acarosporomycetidae, the Verrucariales, the Arthoniomycetidae and the Lichinales. The genes recovered were included in a refined phylogenetic analysis. The hypothesis that lichens symbiotic with a nitrogen-fixing cyanobacterium as a primary photobiont or lichens living in high nitrogen environments lose the plant-like ammonium transporters was upheld, but did not account for additional losses of ammonium transporters/ammonia permeases in the lichens from the Acarosporomycetidae, Chaetotheriomycetes and Arthoniomycetes. In addition, the four ammonium transporter/ammonia permease genes from Cladonia grayi were shown to be functional by expressing the lichen genes in a strain of Saccharomyces cerevisiae in which all three native ammonium transporters were deleted, and assaying for growth on limiting ammonia as a sole nitrogen source.ConclusionsGiven sufficient coverage, next-generation sequencing technology can definitively address the loss of a gene in a genome when using environmental DNA isolated from lichen thalli collected from their natural habitats. Lichen-forming fungi have been losing ammonium transporters/ammonia permease genes at a slower rate than the most closely related non-lichenized lineages. These horizontally transferred genes in the Cladonia grayi genome encode functional ammonium transporters/ammonia permeases.

【 授权许可】

CC BY   
© McDonald et al.; licensee BioMed Central Ltd. 2013