The Effect of Thermopriming on Transcriptional Response of Heat Stress Memory in Rapeseed

Heat stress has detrimental effects on the growth and performance of plants through biochemical, physiological, morphological, and molecular changes. Plants have developed complex mechanisms to balance growth and tolerance to stress, allowing them to effectively defend against more severe stresses by remembering mild stress and forming heat stress memory, known as thermopriming. To investigate the role of thermopriming in inducing the transcription response of HSFA2, HSFA1b and MIPS2 genes, the changes in the transcriptional level of the genes were studied at different times after priming and return stress in canola seedlings using the qRT-PCR technique. The results showed that the expression of these genes was not stable during the recovery period after the initial mild stress (memory phase), while their transcription level immediately after facing the second severe stress was induced at a much higher level in primed plants (P+T treatment) compared to non-primed plants (T treatment) which continued until 48 hours after return stress. Also, morphological analysis of seedlings at 7 and 14 days after release from the second stress showed that thermopriming increase the growth indices and heat tolerance in these plants through strengthening the expression of stress memory genes. Since the HSFA1b, HSFA2 and MIPS2 genes have maintained their expression level until days after the return stress, these genes can be the key components of the transcriptional memory of heat stress and be used in breeding programs and the development of heat tolerant varieties.