Journal Article

Structural polymorphisms and distinct genomic composition suggest recurrent origin and ongoing evolution of B chromosomes in the Prospero autumnale complex (Hyacinthaceae)

Parker, John S, Jang, Tae‐Soo, Weiss‐Schneeweiss, Hanna

2016

Overview

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 DNAs, 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 rDNAs 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 DNAs. Bs were structurally variable and highly enriched in 5S rDNA and satDNA 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.

• Publisher: Academic Press,New Phytologist Trust,Wiley Subscription Services, Inc,John Wiley and Sons Inc
• Subject: Asparagaceae / Asparagaceae - genetics / Biological Evolution / B‐chromosome evolution / B‐chromosome painting / chromosome aberrations / chromosome mapping / Chromosome rearrangements / Chromosomes / Chromosomes, Plant - genetics / Composition / cytotypes / Deoxyribonucleic acid / Diploids / Diploidy / DNA / DNA, Ribosomal - genetics / DNA, Satellite - genetics / Evolution / fluorescence in situ hybridization (FISH) / genome / Genome, Plant / Genomes / Genomic in situ hybridization / genomic in situ hybridization (GISH) / Genomics / Hybridization / Hybrids / in situ hybridization / In Situ Hybridization, Fluorescence / Localization / Meiosis - genetics / Ploidy / Polymorphism, Genetic / polyploids / Polyploidy / Prospero autumnale complex / rDNA (5S and 35S rDNA) / Recombination / ribosomal DNA / Satellite DNA / satellite DNA PaB6 / Supernumerary / Tandem Repeat Sequences - genetics