Abstract
Meiotic recombination ensures accurate homologous chromosome segregation during meiosis and generates novel allelic combinations among gametes. During meiosis, DNA double strand breaks (DSBs) are generated to facilitate recombination. To maintain genome integrity, meiotic DSBs must be repaired using appropriate DNA templates. Although the DNA damage response protein kinase Ataxia-telangiectasia mutated (ATM) has been shown to be involved in meiotic recombination in Arabidopsis, its mechanistic role is still unclear. In this study, we performed cytological analysis in Arabidopsis atm mutant, we show that there are fewer γH2AX foci, but more RAD51 and DMC1 foci on atm meiotic chromosomes. Furthermore, we observed an increase in meiotic Type I crossovers (COs) in atm. Our genetic analysis shows that the meiotic phenotype of atm rad51 double mutants is similar to the rad51 single mutant. Whereas, the atm dmc1 double mutant has a more severe chromosome fragmentation phenotype compared to both single mutants, suggesting that ATM functions in concert with RAD51, but in parallel to DMC1. Lastly, we show that atm asy1 double mutants also have more severe meiotic recombination defects. These data lead us to propose a model wherein ATM promotes RAD51-mediated meiotic DSB repair by inter-sister-chromatid (IS) recombination in Arabidopsis.
Highlights
Meiosis is a fundamental biological process during sexual reproduction in eukaryotes that generates haploid gametes in preparation for fertilization
To identify genes that regulate meiotic recombination, we screened a Ds insertion library generated in Landsberg erecta (Ler) Arabidopsis (Sundaresan et al, 1995), seeking sterile plants with meiotic defects
It is possible that the decrease in γH2AX foci number in atm is due to unphosphorylated H2AX around double strand breaks (DSBs), and does not reflect the true number of meiotic DSBs
Summary
Meiosis is a fundamental biological process during sexual reproduction in eukaryotes that generates haploid gametes (sperms and eggs) in preparation for fertilization. Meiotic recombination is initiated by the formation of DNA double strand breaks (DSBs) which are catalyzed by the conserved topoisomerase-like protein SPO11 (Grelon et al, 2001; Stacey et al, 2006). These DSBs are processed by the MRN (MRE11-RAD50-NBS1) complex to create. There are ∼150– 250 DSBs in each Arabidopsis meiosis, but only ∼9–10 COs (Copenhaver et al, 1998; Serrentino and Borde, 2012; Choi et al, 2018). DSBs that are not repaired as COs are repaired by inter-homolog recombination as NCOs or inter-sister-chromatid recombination (Lu et al, 2012; Wijnker et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
