Fast and Precise: How to Measure Meiotic Crossovers in Arabidopsis

Abstract

During meiosis, homologous chromosomes (homologs) pair and undergo genetic recombination via assembly and disassembly of the synaptonemal complex. Meiotic recombination is initiated by excess formation of DNA double-strand breaks (DSBs), among which a subset are repaired by reciprocal genetic exchange, called crossovers (COs). COs generate genetic variations across generations, profoundly affecting genetic diversity and breeding. At least one CO between homologs is essential for the first meiotic chromosome segregation, but generally only one and fewer than three inter-homolog COs occur in plants. CO frequency and distribution are biased along chromosomes, suppressed in centromeres, and controlled by pro-CO, anti-CO, and epigenetic factors. Accurate and high-throughput detection of COs is important for our understanding of CO formation and chromosome behavior. Here, we review advanced approaches that enable precise measurement of the location, frequency, and genomic landscapes of COs in plants, with a focus on Arabidopsis thaliana .

Evaluation of Crossover Number, Distribution, and Interference Using Cytological Assays in Arabidopsis

“…Since then, cytological methods, such as chromosome spreading, fluorescence in situ hybridization (FISH), and immunostaining, have been developed as classical and efficient approaches to interrogate meiosis and meiotic recombination in vivo (Armstrong, Sanchez‐Moran, & Franklin, 2009; Chelysheva et al., 2010; Wang, Cheng, Lu, Timofejeva, & Ma, 2014). Conventionally, CO interference quantification requires time‐consuming procedures, such as the generation of genome‐wide sets of pollen fluorescence‐tagged lines (FTLs) or construction of F 2 segregation populations (Kim & Choi, 2022) for monitoring meiotic recombination. By contrast, cytological assays have become convenient and effective approaches to analyze the number and distribution of COs and CO interference during meiosis (Armstrong, Caryl, Jones, & Franklin, 2002; Sanchez Moran, Armstrong, Santos, Franklin, & Jones, 2001).…”

Unlocking the secrets of Brassica oleracea crops : A genomic journey

“…In addition, COs drive genetic exchange between homologous chromosomes, which generates novel allelic combinations and genetic diversity among offspring (Fernandes et al, 2018, Wang and. The first step towards understanding the underlying mechanism of CO formation is to accurately detect COs. To date, several approaches have been developed to measure the location and frequency of COs in plants, including immunocytological analyses, fluorescence-tagged lines (FTLs) systems and sequencing-based methods (reviewed in Kim and Choi, 2022) (Kim and Choi, 2022). COs can be cytologically detected by counting the number of chiasmata from pollen mother cells (PMCs) based on the bivalent shape using fluorescence in situ hybridization (FISH) staining of specific regions or whole chromosomes (Moran et al, 2001, Sanchez-Moran et al, 2002, López et al, 2012.…”