*4.1. Plant Materials*

Seeds of two Chinese cabbage (*Brassica rapa* ssp. *pekinensis*) inbred lines, Chiifu and Kenshin, were kindly provided by Woori Seed Co., Sejong City, Korea. The seeds were sown in a 32-hole tray (6 × 6 × 6 cm × 32 holes) and grown for approximately 3 weeks in a growth chamber at 22 ◦C under a 16 h light/8 h dark photoperiod with a photon flux density of 140 µmol m−<sup>2</sup> s −1 . For warming treatment, the plants were subjected to 12 ◦C for 2 days under the same photoperiod and transferred to 28 ◦C for 3 h. For extreme HS treatment, warming-exposed plants were further incubated at 45 ◦C in a growth chamber for 3 h. The samples were collected at the end of each treatment (Figure 1). Humidity of growth chambers was set to 70 ± 10%. Shoots from five individual plants were sampled and quickly frozen in liquid nitrogen. To prepare the other experimental samples, plants grown for 3 weeks were subjected to various temperature treatments.
