ATM-Mediated Double-Strand Break Repair Is Required for Meiotic Genome Stability at High Temperature.

In eukaryotes, meiotic recombination maintains genome stability and creates genetic diversity. The conserved kinase Ataxia Telangiectasia Mutated (ATM) regulates multiple processes in meiotic homologous recombination including DNA double-strand break (DSB) formation and repair, synaptonemal complex organization, and crossover formation and distribution. However, its function in plant meiotic recombination at stressful environmental conditions remain poorly understood. In this study, we demonstrate that ATM is required for maintenance of meiotic genome stability under heat stress in Arabidopsis thaliana. By using cytogenetic approaches, we determined that ATM does not mediate the reduced DSB formation but ensures successful DSB repair and thus meiotic chromosome integrity under heat stress. Further genetic analysis suggested that ATM mediates DSB repair at high temperature by acting downstream of the MRE11-RAD50-NBS1 (MRN) complex, and acts in a RAD51-independent but chromosome axis-dependent manner. This study extends our understanding on the role of ATM in DSB repair and protection of genome stability in plants under high temperature stress.