Massive crossover elevation via combination of HEI10 and recq4a recq4b during Arabidopsis meiosis

Abstract

During meiosis, homologous chromosomes undergo reciprocal crossovers, which generate genetic diversity and underpin classical crop improvement. Meiotic recombination initiates from DNA double-strand breaks (DSBs), which are processed into single-stranded DNA that can invade a homologous chromosome. The resulting joint molecules can ultimately be resolved as crossovers. In , competing pathways balance the repair of ∼100-200 meiotic DSBs into ∼10 crossovers per meiosis, with the excess DSBs repaired as noncrossovers. To bias DSB repair toward crossovers, we simultaneously increased dosage of the procrossover E3 ligase gene and introduced mutations in the anticrossovers helicase genes and As and increase interfering and noninterfering crossover pathways, respectively, they combine additively to yield a massive meiotic recombination increase. Interestingly, we also show that increased dosage increases crossover coincidence, which indicates an effect on interference. We also show that patterns of interhomolog polymorphism and heterochromatin drive recombination increases distally towards the subtelomeres in both and backgrounds, while the centromeres remain crossover suppressed. These results provide a genetic framework for engineering meiotic recombination landscapes in plant genomes.

A rigorous measure of genome-wide genetic shuffling that takes into account crossover positions and Mendel’s second law

“…One category of hypotheses invokes mechanical advantages of spread-out crossovers, either to bivalent stability in prophase [134] or to homolog segregation at meiosis I [135]. However, such ideas are challenged by the fact that meiotic segregation proceeds without trouble in organisms that lack crossover interference (e.g., fission yeast and Aspergillus [136]) or that have had interference experimentally reduced or eliminated [137,138]. The present study raises the possibility of a qualitatively different idea, that crossover interference provides an evolutionary advantage via its effects on genetic transmission.…”

Chromosome-level assemblies of multiple Arabidopsis genomes reveal hotspots of rearrangements with altered evolutionary dynamics

“…In contrast, meiotic recombination in Arabidopsis was shown to be supressed by structural diversity 37 . To test if HRs are indeed depleted for meiotic recombination, we overlapped rearranged regions with 15,683 crossover (CO) sites previously identified within Col-0/Ler F2 progenies 37,38 . Only 64 of them partially overlapped with non-syntenic regions while all other COs were found in syntenic regions (Fig.…”

“… (a) Crossover (CO) breakpoints 37,38 identified in Col-0 x L er hybrids were checked for their overlaps in syntenic or rearranged regions. Only unique CO intervals smaller than 5kb were used.…”

DeepTetrad: high-throughput analysis of meiotic tetrads by deep learning in plants

“…The remaining ∼10–15% of COs are non-interfering and occur via the Type II pathway 10 . Non-interfering COs are resolved by the MUS81 endonuclease and are restricted by anti-recombination factors such as FANCM, RECQ4A, RECQ4B, and FIGL1 11–15 . Disruption of anti-recombination factors can increase the number of Type II COs in plants, which has the potential to create new combinations of desirable alleles that can improve crop varieties 13,16 .…”