2.1 BRs play a positive role in thermomemory
To elucidate the role of BRs in thermomemory in Arabidopsis , we performed a thermotolerance assay under primed and unprimed conditions towards wild-type Col-0. Heat priming and triggering protocol was outlined in Fig. 1A. Seedlings grown on standard half-strength Murashige-Skoog (1/2MS) medium with or without 10 nM BL (brassinolide, a kind of BRs with high physiological activity) were vibrant before HS. Upon HS triggering and recovery, seedlings grown on the medium containing BL exhibited significantly enhanced thermotolerance, accompanied with comparably elevated survival rate and decreased electrolyte leakage. Thermomemory induced by heat priming effectively improved the thermotolerance of seedlings and the application of BL further enhanced the vitality of thermomemory (Fig. 1). These observations suggest that BRs positively modulate thermomemory process.