The characterisation of mutant lines can help elucidate how recombination is controlled. We used a combination of genetic segregation analysis, cytogenetics, immunocytology and 3D imaging to genetically map and characterize the barley meiotic mutant DESYNAPTIC 10 (des10).
We identified a natural exonic deletion in the ortholog of MutL-Homolog 3 (HvMlh3) as the causal lesion. Compared to wild-type, des10 mutants exhibit reduced recombination and fewer chiasmata, resulting in the loss of obligate crossovers and leading to chromosome mis-segregation. Using 3D-SIM, we observed that normal synapsis progression was also disrupted in des10, a phenotype that was not evident with standard confocal microscopy and that has not been reported with Mlh3 knock-39 out mutants in Arabidopsis.
Our data provide new insights on the interplay between synapsis and recombination in barley and highlight the need for detailed studies of meiosis in non-model species. This study also confirms the importance of early stages of prophase I for the control of recombination in large genome cereals.