Abstract
Old World lupins constitute an interesting model for evolutionary research due to diversity in genome size and chromosome number, indicating evolutionary genome reorganization. It has been hypothesized that the polyploidization event which occurred in the common ancestor of the Fabaceae family was followed by a lineage-specific whole genome triplication (WGT) in the lupin clade, driving chromosome rearrangements. In this study, chromosome-specific markers were used as probes for heterologous fluorescence in situ hybridization (FISH) to identify and characterize structural chromosome changes among the smooth-seeded (Lupinus angustifolius L., Lupinus cryptanthus Shuttlew., Lupinus micranthus Guss.) and rough-seeded (Lupinus cosentinii Guss. and Lupinus pilosus Murr.) lupin species. Comparative cytogenetic mapping was done using FISH with oligonucleotide probes and previously published chromosome-specific bacterial artificial chromosome (BAC) clones. Oligonucleotide probes were designed to cover both arms of chromosome Lang06 of the L. angustifolius reference genome separately. The chromosome was chosen for the in-depth study due to observed structural variability among wild lupin species revealed by BAC-FISH and supplemented by in silico mapping of recently released lupin genome assemblies. The results highlighted changes in synteny within the Lang06 region between the lupin species, including putative translocations, inversions, and/or non-allelic homologous recombination, which would have accompanied the evolution and speciation.
Highlights
Legumes (Fabaceae Lindl.) are the third largest family of higher plants with approximately20,000 species, and second as to the harvested area and total production of 300 million metric tons of grain legumes on 190 million ha [1]
The chromosome region should exhibit at least partial differentiation in related species, evidenced by previous cytogenetic studies or genome/linkage mapping; The chromosome region should have a low abundance of repetitive elements to allow the design of unique probes; Scaffolding in this region should be strongly supported by linkage mapping to avoid unintentional incorporation of fragments from other chromosomes; Chromosome-specific cytogenetic landmarks (i.e., bacterial artificial chromosome (BAC) clones) should be available for this region to enable parallel use of two techniques—BAC-fluorescence in situ hybridization (FISH) and oligo-FISH
Considering BAC-FISH results obtained in previous studies [17,35] and comparative mapping of
Summary
Legumes (Fabaceae Lindl.) are the third largest family of higher plants with approximately20,000 species, and second as to the harvested area and total production of 300 million metric tons of grain legumes on 190 million ha [1]. The family is diverse in many aspects, including plant morphology, habitat, and ecology, as well as genome size and evolution [2,3]. It has been assumed that the genome complexity and species diversity were promoted by whole-genome duplications (WGDs), which occurred in ancient legumes before the major diversification events [4]. The WGDs were further followed by polyploidization(s) in particular lineages, advancing their further expansions [5,6,7,8,9]. This is a typical evolutionary scenario, which is believed to have occurred in many angiosperm clades.
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