Selfish supernumerary chromosome reveals its origin as a mosaic of host genome and organellar sequences

Mihaela Maria Martis, Sonja Klemme, Ali Mohammad Banaei-Moghaddam, Frank R. Blattner, Jiř́i Macas, Thomas Schmutzer, Uwe Scholz, Heidrun Gundlach, Thomas Wicker, Hana Sǐmková, Petr Novaḱ, Pavel Neumann, Marie Kubalaḱová, Eva Bauer, Grit Haseneyer, Jörg Fuchs, Jaroslav Dolezěl, Nils Stein, Klaus F.X. Mayer, Andreas Houben

Research output: Contribution to journalArticlepeer-review

151 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)13343-13346
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number33
Publication statusPublished - 14 Aug 2012
Externally publishedYes


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