*3.1. Transcriptome Analysis*

Of the three treatments, both warming and minor-warming conditions upregulated genes enriched in five biological process categories in both inbred lines, including "response to heat", "heat acclimation", and "response to temperature stimulus" (Figures 2 and 3), indicating that the general responses of both lines are similar. However, genes involved in "response to auxin stimulus" were upregulated by both warming and minor warming in Kenshin, but not in Chiifu. This category of genes might be important for HT adaptation in Chinese cabbage. There is increasing evidence for an association between HT and auxin responses—HT reduces auxin biosynthesis [28], and HSPs such as sHSP22 [29] and cytosolic HSP90 [30] regulate auxin responses.

Our transcriptome analysis indicated that *BrHSFA2* was upregulated or induced in both lines under all three treatment conditions (LT, warming, and minor warming). *Arabidopsis HSFA2* is induced by HT and plays a role in the maintenance of HS memory [26,31,32]. *Arabidopsis HSFA2* expression is also associated with H2O2/ROS stress [33] and salt/osmotic stress [34], suggesting that it plays an important role in responses to various stress conditions. The induction of *BrHSFA2* expression by LT treatment suggests that BrHSFA2 targets LT-responsive genes besides HSR genes upon exposure to HT.
