Rumex hastatulus: one species, two karyotypes
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| Year of publication | 2024 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | Chromosomal rearrangements play a crucial role in the evolution of new species. It is known that sex chromosomes are inequitably associated with genomic divergence and may serve as drivers for speciation. Nonetheless, the exact role of sex chromosomes in the formation of reproductive isolation remains unclear. Plant species with newly evolved sex chromosomes are excellent models to study the early events of speciation. Rumex hastatulus is a dioecious flowering weed native to North America. This plant species differs cytologically depending on their geographical location and evolutionary history. Male plants to the west of the Mississippi River, Texas (Tx) race, have a telocentric X and one large Y chromosome, plants to the east of the River, North Carolina (NC) race, have undergone chromosomal rearrangements resulting in a larger X and two Y chromosomes. This makes R. hastatulus an ideal model to decipher how heteromorphic sex chromosomes influence the level of genomic divergence in plants. Using the combination of phased assembly with subsequent repeatome analysis and physical localization of robust tandem repeats, we found substantial differences between NC and Tx races at the chromosomal level. Our results revealed that the neo-sex chromosome system of NC underwent at least two fusions between the sex chromosomes and one pair of autosomes. We found the Y chromosome was broken multiple times and there is strong evidence of significant reorganization on autosomes in the newly formed NC karyotype. This demonstrates that sex chromosome-autosomal fusions and autosomal inversion(s) are the first steps in the establishment of reproductive isolation. Furthermore, the existence of the hybrid zone between both races and the knowledge of genome evolution offers a unique opportunity to investigate the (epi)genetic background behind the genomic divergence and speciation. |
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