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

ABSTRACT 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 further understand temperature effects on meiosis, we have followed male meiocytes of Arabidopsis thaliana by live cell imaging under three different temperature regimes, at 21°C and at heat shock conditions of 30°C and 34°C as well as after an acclimatization phase of one week at 30°C. This work led to a cytological framework of meiotic progression at elevated temperature. We found that an increase to 30°C, sped up meiotic progression with specific phases being more amenable to heat than others. An acclimatization phase often moderated this effect. A sudden increase to 34°C promoted a faster progression of meiosis in early prophase compared to 21°C. However, the phase in which cross-overs maturate was found to be prolonged at 34°C. Interestingly, mutants involved in the recombination pathway did not show the extension of this phase at 34°C demonstrating that the delay is recombination dependent. Further analysis revealed the involvement of the ATM kinase in this prolongation indicating the existence of a specialized variant of the pachytene checkpoint in plants.