Heat Priming Modifies Heat Stress Response in BPM1-Overexpressing Arabidopsis thaliana (L.) Heynh.

Rising temperatures due to global warming pose a growing threat to plant metabolism. Priming plants with moderately elevated temperatures prior to severe heat stress (HS) has been shown to increase tolerance to HS. In Arabidopsis thaliana (L.) Heynh. MATH-BTB (BPM) proteins, as part of the proteasomal degradation pathway, modulate plant response to abiotic stress, but there are no data on their role in HS tolerance. Therefore, we investigated the response of BPM1-overexpressing (oeBPM1) and wild-type A. thaliana seedlings exposed to severe HS of 42 degrees C with or without priming at 37 degrees C. This study included the analysis of certain physiological and biochemical parameters, the expression of several heat-inducible genes and the expression of the ONSEN retrotransposon. In both non-primed oeBPM1 and wild-type seedlings, HS led to severe damage despite induced expression of HS-responsive genes, including DREB2A, HSFA3 and HSP90. Priming resulted in up-regulation of HSFA2 stress memory gene, activation of the ONSEN retrotransposon, and preserved photosynthetic performance, followed by long-term survival of both oeBPM1 and wild-type seedlings. However, PCA analysis revealed separation of primed oeBPM1 seedlings from primed wild type due to lower induction of HSFA2 and ONSEN transcript. Moreover, the germination rate of seeds collected from primed oeBPM1 plants was higher than that of wild-type seeds. These results suggest that overexpression of BPM1 contributes to acquired thermotolerance by adjusting responses to adverse temperature conditions. Our research sheds new light on BPM-mediated thermotolerance and highlights the importance of BPM1 overexpression for acquired thermotolerance.