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The Control of the Crossover Localization in Allium

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Submitted:

14 December 2022

Posted:

16 December 2022

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Abstract
Meiotic crossovers/chiasmata are not randomly distributed and strictly controlled. The mechanisms behind COs patterning remain largely unknown. In many species COs predominantly occur in the distal 2/3 of the chromosome arm and suppression of COs is observed in the proximal regions. The exceptions are some species, among which Allium fistulosum has strictly localized COs in the proximal region. The ability to manipulate the COs localization can be useful for onion breeding. We investigated the factors that may contribute to the pattern of COs in two closely related onion species A. cepa and A. fistulosum, which differ significantly in the localization of chiasmata, and their F1 diploid and triploid hybrids in pollen mother cells. We demonstrate a significant shift in the COs localization to the distal and interstitial region in F1 triploid hybrid, which has a complete diploid set of A. fistulosum chromosomes and haploid set of A. cepa chromosomes. This observation points to a possible genetic control of COs distribution. We did not find the differences in the assembly and disassembly of ASY1 and ZYP1 between A. cepa and A. fistulosum while the difference between parental species and their hybrids was observed. In diploid F1 hybrids at pachytene the chromosome pairing delay marked by ASY1 was revealed. Immunolocalization of MLH1, a marker for class I of the interference-dependent COs, and MUS81, a marker for class II of the interference-free COs, and mlh1/mus81 gene expression profiling in different stages of meiosis showed a spatiotemporal asymmetry among A. cepa, A. fistulosum and their diploid and triploid F1 hybrids. Our results support the hypothesis of genetic control of CO distribution as one of the players that affect meiotic recombination and exchange of genomic material.
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Subject: Biology and Life Sciences  -   Biochemistry and Molecular Biology
Copyright: This open access article is published under a Creative Commons CC BY 4.0 license, which permit the free download, distribution, and reuse, provided that the author and preprint are cited in any reuse.
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