Crossover patterning in plants

Abstract

Key message Chromatin state, and dynamic loading of pro-crossover protein HEI10 at recombination intermediates shape meiotic chromosome patterning in plants. Abstract Meiosis is the basis of sexual reproduction, and its basic progression is conserved across eukaryote kingdoms. A key feature of meiosis is the formation of crossovers which result in the reciprocal exchange of segments of maternal and paternal chromosomes. This exchange generates chromosomes with new combinations of alleles, increasing the efficiency of both natural and artificial selection. Crossovers also form a physical link between homologous chromosomes at metaphase I which is critical for accurate chromosome segregation and fertility. The patterning of crossovers along the length of chromosomes is a highly regulated process, and our current understanding of its regulation forms the focus of this review. At the global scale, crossover patterning in plants is largely governed by the classically observed phenomena of crossover interference, crossover homeostasis and the obligatory crossover which regulate the total number of crossovers and their relative spacing. The molecular actors behind these phenomena have long remained obscure, but recent studies in plants implicate HEI10 and ZYP1 as key players in their coordination. In addition to these broad forces, a wealth of recent studies has highlighted how genomic and epigenomic features shape crossover formation at both chromosomal and local scales, revealing that crossovers are primarily located in open chromatin associated with gene promoters and terminators with low nucleosome occupancy.

Coarsening dynamics can explain meiotic crossover patterning in both the presence and absence of the synaptonemal complex

“…Similarly, in C. elegans , it has previously been suggested that the SC functions to prevent exchange of recombination proteins between RIs via the nucleoplasm ( Rog et al, 2017 ; Zhang et al, 2021 ; Zhang et al, 2018 ). Other studies have also recently proposed that nucleoplasm-mediated coarsening can explain CO patterning in Arabidopsis mutants with abolished synapsis, although the dynamics of this process have not been explicitly modelled ( Durand et al, 2022 ; Lloyd, 2023 ). Using our model, we provide a mechanistic explanation for why zyp1 mutants without synapsis lose both CO interference and assurance.…”

Coarsening dynamics can explain meiotic crossover patterning in both the presence and absence of the synaptonemal complex

“…Similarly, in C. elegans , it has previously been suggested that the SC functions to prevent exchange of recombination proteins between RIs via the nucleoplasm (Rog et al, 2017; Zhang et al, 2021, 2018). Other studies have also recently proposed that nucleoplasm-mediated coarsening can explain CO patterning in Arabidopsis mutants with abolished synapsis, although the dynamics of this process have not been explicitly modelled (Durand et al, 2022; Lloyd, 2022). Using our model, we provide a mechanistic explanation for why zyp1 mutants without synapsis lose both CO interference and assurance.…”

The rate of inversion fixation in plant genomes is highly variable

“…Different taxa have diverse genomic properties. Some may have inherently high recombination rate or epigenetic patterns that allow them to harbour chromosomal rearrangements more easily (Henderson 2012; Lloyd 2022). Each species also has its own demographic and selection history.…”