Meiotic recombination gets stressed out: CO frequency is plastic under pressure

•Meiotic crossover (CO) frequency is under homeostatic control.•Meiotic CO frequency can be modulated by extrinsic factors, such as temperature.•The synaptonemal complex, chromatin, and methylation may be critical factors. Meiotic recombination ensures the fertility of gametes and creates novel genetic combinations. Although meiotic crossover (CO) frequency is under homeostatic control, CO frequency is also plastic in nature and can respond to environmental conditions. Most investigations have focused on temperature and recombination, but other external and internal stimuli also have important roles in modulating CO frequency. Even less is understood about the molecular mechanisms that underly these phenomenon, but recent work has begun to advance our knowledge in this field. In this review, we identify and explore potential mechanisms including changes in: the synaptonemal complex, chromatin state, DNA methylation, and RNA splicing.