Heat stress reveals a specialized variant of the pachytene checkpoint in meiosis of Arabidopsis thaliana

Plant growth and fertility strongly depend on environmental conditions such as temperature. Remarkably, temperature also influences meiotic recombination and thus, the current climate change will affect the genetic make-up of plants. To better understand the effects of temperature on meiosis, we followed male meiocytes in Arabidopsis thaliana by live cell imaging under three temperature regimes: at 21 degrees C; at heat shock conditions of 30 degrees C and 34 degrees C; after an acclimatization phase of 1 week at 30 degrees C. This work led to a cytological framework of meiotic progression at elevated temperature. We determined that an increase from 21 degrees C to 30 degrees C speeds up meiosis with specific phases being more amenable to heat than others. An acclimatization phase often moderated this effect. A sudden increase to 34 degrees C promoted a faster progression of early prophase compared to 21 degrees C. However, the phase in which cross-overs mature was prolonged at 34 degrees C. Since mutants involved in the recombination pathway largely did not show the extension of this phase at 34 degrees C, we conclude that the delay is recombination-dependent. Further analysis also revealed the involvement of the ATAXIA TELANGIECTASIA MUTATED kinase in this prolongation, indicating the existence of a pachytene checkpoint in plants, yet in a specialized form.