title: Selfish supernumerary chromosome reveals its origin as a mosaic of host genome and organellar sequences.
abstract: Supernumerary B chromosomes are optional additions to the basic set of A chromosomes, and occur in all eukaryotic groups. They differ from the basic complement in morphology, pairing behavior, and inheritance and are not required for normal growth and development. The current view is that B chromosomes are parasitic elements comparable to selfish DNA, like transposons. In contrast to transposons, they are autonomously inherited independent of the host genome and have their own mechanisms of mitotic or meiotic drive. Although B chromosomes were first described a century ago, little is known about their origin and molecular makeup. The widely accepted view is that they are derived from fragments of A chromosomes and/or generated in response to interspecific hybridization. Through next-generation sequencing of sorted A and B chromosomes, we show that B chromosomes of rye are rich in gene-derived sequences, allowing us to trace their origin to fragments of A chromosomes, with the largest parts corresponding to rye chromosomes 3R and 7R. Compared with A chromosomes, B chromosomes were also found to accumulate large amounts of specific repeats and insertions of organellar DNA. The origin of rye B chromosomes occurred an estimated ∼1.1-1.3 Mya, overlapping in time with the onset of the genus Secale (1.7 Mya). We propose a comprehensive model of B chromosome evolution, including its origin by recombination of several A chromosomes followed by capturing of additional A-derived and organellar sequences and amplification of B-specific repeats.
authors: Institute of Bioinformatics and Systems Biology, German Research Center for Environmental Health, 85764 Neuherberg, Germany.
authors: Mihaela Maria
authors: MM
authors: Martis
authors: Sonja
authors: S
authors: Klemme
authors: Ali Mohammad
authors: AM
authors: Banaei-Moghaddam
authors: Frank R
authors: FR
authors: Blattner
authors: Jiří
authors: J
authors: Macas
authors: Thomas
authors: T
authors: Schmutzer
authors: Uwe
authors: U
authors: Scholz
authors: Heidrun
authors: H
authors: Gundlach
authors: Thomas
authors: T
authors: Wicker
authors: Hana
authors: H
authors: Šimková
authors: Petr
authors: P
authors: Novák
authors: Pavel
authors: P
authors: Neumann
authors: Marie
authors: M
authors: Kubaláková
authors: Eva
authors: E
authors: Bauer
authors: Grit
authors: G
authors: Haseneyer
authors: Jörg
authors: J
authors: Fuchs
authors: Jaroslav
authors: J
authors: Doležel
authors: Nils
authors: N
authors: Stein
authors: Klaus F X
authors: KF
authors: Mayer
authors: Andreas
authors: A
authors: Houben
mesh_terms: D001483:Base Sequence; D002503:Centromere / Q000235:genetics; D032461:Chromosomes, Plant / Q000235:genetics*; D019143:Evolution, Molecular; D017343:Genes, Plant / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008677:Metaphase / Q000235:genetics; D008957:Models, Genetic; D009030:Mosaicism; D015388:Organelles / Q000235:genetics*; D018626:Retroelements / Q000235:genetics; D012434:Secale / Q000235:genetics*
chemical_list: D018626:Retroelements