Abstract
The shuffling of genetic material facilitated by meiotic crossovers is a critical driver of genetic variation. Therefore, the number and positions of crossover events must be carefully controlled. In Arabidopsis, an obligate crossover and repression of nearby crossovers on each chromosome pair are abolished in mutants that lack the synaptonemal complex (SC), a conserved protein scaffold. We use mathematical modelling and quantitative super-resolution microscopy to explore and mechanistically explain meiotic crossover pattering in Arabidopsis zyp1 mutants, that lack an SC. We develop an SC mutant coarsening model in which crossover precursors globally compete for a limited pool of the pro-crossover factor HEI10, with dynamic HEI10 exchange mediated through the nucleoplasm. We demonstrate that this model is capable of quantitatively reproducing and predicting experimental crossover patterning and HEI10 foci intensity data. Our results reveal that regulation of the number of crossovers within a cell in SC mutants (“trans-interference”), and inhibition of nearby crossovers on the same chromosome in wild-type cells (“cis-interference”), likely act through the same underlying coarsening mechanism, differing only in the spatial compartment through which the pro-crossover factor diffuses. The spatial compartment used is controlled by the SC, which therefore acts as a critical regulator of cis- versus trans-interference.
Competing Interest Statement
The authors have declared no competing interest.
