Meiotic recombination in plants: controlling the transition of DNA double-strand breaks to genetic crossovers

Genetic variation generated through the process of homologous recombination (HR) during meiosis underpins plant breeding and efforts to deliver the rapid improvements in crops that will be required to ensure Food Security into the foreseeable future. HR is initiated by the programmed formation of DNA double-strand breaks (DSBs) by the SPO11 complex. DSBs are processed by components of the HR pathway and are repaired as crossovers (COs), which recombine the homologous parental chromosomes, or non-crossovers (NCOs), where only short stretches of DNA are exchanged. In plants most DSBs (90%+) are repaired as NCOs1. This limits the genetic variation that is generated in each meiotic division. Moreover, the distribution of COs, notably in cereal crops, is skewed towards particular chromosomal regions. The extensive work and collaborative efforts of the MEIOREC investigators have led to significant progress in understanding the basis of these limitations and have made headway in addressing them1. Nevertheless, full understanding of how the transition of a DSB to yield a CO is controlled at a particular genomic locus and how this can be optimized remains a major challenge. We believe that the combined expertise of MEIOREC consortium provides a real opportunity to make substantial progress in addressing this important problem. Controlled formation of meiotic COs involves a coordinated programme whereby DSBs are channelled through a series of transitions to form either CO or NCO products.
The aim of MEIOREC is to decipher the DSB to CO transitional steps and evaluate strategies to manipulate CO formation using model species thereby laying the foundation for subsequent translation of the most promising into crops. This will be implemented by a set of workpackages (WPs) with specific scientific objectives (SOs): WP1: Factors controlling DSB formation; WP2: DSB processing and CO resolution; WP3: Relationship of chromosome remodelling and CO formation.