title: Next generation sequencing reveals genome downsizing in allotetraploid Nicotiana tabacum, predominantly through the elimination of paternally derived repetitive DNAs.
abstract: We used next generation sequencing to characterize and compare the genomes of the recently derived allotetraploid, Nicotiana tabacum (<200,000 years old), with its diploid progenitors, Nicotiana sylvestris (maternal, S-genome donor), and Nicotiana tomentosiformis (paternal, T-genome donor). Analysis of 14,634 repetitive DNA sequences in the genomes of the progenitor species and N. tabacum reveal all major types of retroelements found in angiosperms (genome proportions range between 17-22.5% and 2.3-3.5% for Ty3-gypsy elements and Ty1-copia elements, respectively). The diploid N. sylvestris genome exhibits evidence of recent bursts of sequence amplification and/or homogenization, whereas the genome of N. tomentosiformis lacks this signature and has considerably fewer homogenous repeats. In the derived allotetraploid N. tabacum, there is evidence of genome downsizing and sequences loss across most repeat types. This is particularly evident amongst the Ty3-gypsy retroelements in which all families identified are underrepresented in N. tabacum, as is 35S ribosomal DNA. Analysis of all repetitive DNA sequences indicates the T-genome of N. tabacum has experienced greater sequence loss than the S-genome, revealing preferential loss of paternally derived repetitive DNAs at a genome-wide level. Thus, the three genomes of N. sylvestris, N. tomentosiformis, and N. tabacum have experienced different evolutionary trajectories, with genomes that are dynamic, stable, and downsized, respectively.
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Renny-Byfield
authors.forename: Michael
authors.initials: M
authors.lastname: Chester
authors.forename: Ales
authors.initials: A
authors.lastname: Kovařík
authors.forename: Steven C
authors.initials: SC
authors.lastname: Le Comber
authors.forename: Marie-Angèle
authors.initials: MA
authors.lastname: Grandbastien
authors.forename: Marc
authors.initials: M
authors.lastname: Deloger
authors.forename: Richard A
authors.initials: RA
authors.lastname: Nichols
authors.forename: Jiri
authors.initials: J
authors.lastname: Macas
authors.forename: Petr
authors.initials: P
authors.lastname: Novák
authors.forename: Mark W
authors.initials: MW
authors.lastname: Chase
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Leitch
mesh_terms: D016000:Cluster Analysis; D019143:Evolution, Molecular; D018628:Gene Dosage; D059646:Genome Size; D018745:Genome, Plant; D059014:High-Throughput Nucleotide Sequencing; D019684:Magnoliopsida / Q000235:genetics; D011123:Polyploidy; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D014026:Nicotiana / Q000235:genetics*