Most cited article - PubMed ID 37428465
The meso-octoploid Heliophila variabilis genome sheds a new light on the impact of polyploidization and diploidization on the diversity of the Cape flora
Understanding the relationship between macro- and microevolutionary processes and their delimitation remains a challenge. This review focuses on the role of chromosomal rearrangements in plant population differentiation and lineage diversification resulting in speciation, helping bridge the gap between macro- and microevolution through chromosomal evolution. We focus on angiosperms, a group that comprises the majority of extant plant species diversity and exhibits the largest chromosomal and genomic variations. Here, we address the following questions: Are macroevolutionary patterns of chromosome evolution the result of accumulated microevolutionary changes, or do chromosomal dynamics drive larger shifts along the speciation continuum? At the macroevolutionary level, we investigated the association between karyotype diversity and diversification rates using evidence from comparative genomics, chromosomal evolution modelling across phylogenies, and the association with several traits across different angiosperm lineages. At the microevolutionary level, we explore if different karyotypes are linked to morphological changes and population genetic differentiation in the same lineages. Polyploidy (autopolyploidy and allopolyploidy) and dysploidy are known drivers of speciation, with karyotypic differences often leading to reproductive barriers. We found that dysploidy, involving gains and losses of single chromosomes with no significant change in overall content of the genome, appears to be relatively more frequent and persistent across macroevolutionary histories than polyploidy. Additionally, chromosomal rearrangements that do not entail change in chromosome number, such as insertions, deletions, inversions, and duplications of chromosome fragments, as well as translocations between chromosomes, are increasingly recognized for their role in local adaptation and speciation. We argue that there is more evidence linking chromosomal rearrangements with genetic and morphological trait differentiation at microevolutionary scales than at macroevolutionary ones. Our findings highlight the importance of selection across evolutionary scales, where certain chromosomal dynamics become fixed over macroevolutionary time. Consequently, at microevolutionary scales, chromosome rearrangements are frequent and diverse, serving as key drivers of plant diversification and adaptation by providing a pool of variation from which beneficial chromosomal changes can be selected and fixed by evolutionary forces.
- Keywords
- angiosperms, chromosome, dysploidy, evolution, polyploidy, speciation,
- Publication type
- Journal Article MeSH
- Review MeSH
Boechera falcata (Turcz.) Al-Shehbaz, previously known as Arabis turczaninowii Ledeb., is a herbaceous perennial of the East Siberian, boreal-steppe ecotype. It is the sole species of the diverse genus Boechera found on the Eurasian continent, with all other species endemic to North America and Greenland. Likely migrating from North America to Eastern Siberia via the Bering Land Bridge during the Pleistocene glaciation, B. falcata presents a unique case for genomic study. The genus Boechera is notable for its many allodiploid and triploid apomicts, which have arisen through complex hybridization of sexual species and ecotypes. To date, only the genomes of 2 American Boechera species, B. stricta and B. retrofracta, have been sequenced and analyzed. In this study, we sequenced, assembled to the chromosome level, and analyzed the highly homozygous 189.36 Mb genome of B. falcata (2n = 14). Molecular phylogenetic analysis of nuclear and organelle genomes revealed a high degree of relatedness to North American relatives. Cytogenetic analysis identified all 22 genomic blocks of crucifers, showing that 5 of the 7 B. falcata chromosomes are collinear with their ancestral counterparts, while 2 have undergone inversions. Allelic analysis of the apomixis marker APOLLO gene revealed that B. falcata contains only sex alleles. The availability of the B. falcata genome will advance studies of the evolution and phylogeny of Brassicaceae species and the mechanisms of apomixis, providing a crucial resource for future research in plant genetics and breeding.
- Keywords
- Boechera falcata, Brassicaceae, chloroplast genome, chromosome rearrangements, chromosome-level genome assembly and annotation, comparative chromosome painting, genome structure, molecular phylogeny,
- MeSH
- Brassicaceae * genetics classification MeSH
- Chromosomes, Plant genetics MeSH
- Phylogeny * MeSH
- Genome, Plant * MeSH
- Genomics * methods MeSH
- Publication type
- Journal Article MeSH
The ancestral crucifer karyotype and 22 conserved genomic blocks (CGBs) facilitate phylogenomic analyses in the Brassicaceae. Chromosomal rearrangements reshuffled CGBs of ancestral chromosomes during karyotype evolution. Here, we identify eight protochromosomes representing the common ancestral karyotype (ACBK) of the two Brassicoideae supertribes: Camelinodae (Lineage I) and Brassicodae (Lineage II). The characterization of multiple cascading fusion events allows us to infer evolutionary relationships based on these events. In the Camelinodae, the ACBK first evolved into the AKI genome, which remained conserved in the Cardamineae, whereas it was altered to tAKI by a reciprocal translocation that preceded the diversification of most Camelinodae tribes. The identified fusion breakpoints largely overlap with CGB boundaries, suggesting that CGBs are mainly disrupted by chromosome fusions. Our results demonstrate the stable inheritance of chromosome fusions and their importance for reconstructing evolutionary relationships. The chromosomal breakpoint approach provides a basis for ancestral state reconstruction based on chromosome-level genome assemblies.
