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Structural polymorphisms and distinct genomic composition suggest recurrent origin and ongoing evolution of B chromosomes in the Prospero autumnale complex (Hyacinthaceae)
Author(s) -
Jang TaeSoo,
Parker John S.,
WeissSchneeweiss Hanna
Publication year - 2016
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13778
Subject(s) - biology , ploidy , genetics , polyploid , concerted evolution , genome , plant evolution , karyotype , genome evolution , hybrid , genomic dna , evolutionary biology , chromosome , dna , gene , botany
Summary Supernumerary B chromosomes (Bs) are genomic parasitic components, originating from the A complement via chromosomal rearrangements, which follow their own evolutionary trajectories. They often contain repetitive DNA s, some shared with regular chromosomes and some newly evolved. Genomic composition, origin and evolution of Bs have been analysed in the chromosomally variable Prospero autumnale complex. Two rDNA s and a satellite DNA ( PaB6 ) from regular chromosomes were mapped to Bs of 26 plants from three diploid cytotypes, their hybrids and polyploid derivatives. In homoploid diploid hybrids, genomic in situ hybridization ( GISH ) allowed B painting with the parental DNA s. Bs were structurally variable and highly enriched in 5S rDNA and sat DNA PaB6 , and rarely in 35S rDNA . Eleven combinations of rDNA and PaB6 localization were observed. The quantities of PaB6 in Bs and regular chromosomes were not correlated, suggesting amplification mechanisms other than recombination. PaB6 and 5S rDNA amounts increased with increasing ploidy level. GISH revealed two independent origins of Bs. The structural variation, repeat content, repeat‐type fluctuations and differing genomic affinities of Bs in different cytotypes suggest that they represent young proto‐B chromosomes. Bs in P. autumnale probably form recurrently as by‐products of the extensive genome restructuring within this chromosomally variable species complex.