*4.4. Plant Materials and Treatments*

The kiwifruit cultivar "Jinkui" (*Actinidia chinensis* var. *deliciosa*) were maintained in vitro on Murashige and Skoog (MS) medium supplied with 6-benzylaminopurine (6-BA, 3.0 mg/L, Sigma-Aldrich, St. Louis, MO, USA), and naphthalene acetic acid (NAA, 0.2 mg·L −1 , Sigma) under a 16/8 h photoperiod (100 µmol m−<sup>2</sup> ·s −1 ) at 25 ◦C in a growth chamber. Four-week-old plants were used for hormones, freezing (4 ◦C), and heat stress treatments. Shoots with good growth vigor were collected from Jinkui kiwifruit trees and cultured in MS medium, and maintained in growth chambers, then used for *Pseudomonas syringae* pv. *actinidiae* (Psa) treatments. The conditions included a temperature of 25 ◦C and 12/12 h light/dark cycles. Two-year-old Jinkui cutting seedlings, which were used for salt treatment, were grown in nutrient soil in a greenhouse at a temperature of 25–28 ◦C during the day and 20–25 ◦C during the night.

Several of the stress treatments were performed in kiwifruit as described previously [55]. For treatments with abscisic acid (ABA), 1-aminocyclopropanecarboxylic acid (ACC), salicylic acid (SA) and jasmonic acid (JA), plants with eight fully expanded leaves per tissue-culture container (240 mL) were sprayed with 0.01 mM ABA, 0.01 mM ACC, 0.1 mM SA, and 0.02 mM JA. All the chemicals were purchased from Sigma-Aldrich and dissolved in sterile distilled water. The leaves were harvested at 0, 4, 12, and 48 h post-treatment. For cold stress, seedlings were grown at 4 ◦C for 0, 4, 12, and 48 h. For heat stress, seedlings were grown at 48 ◦C for 0, 2, and 4 h, and then at 24 ◦C for another 6 h. For salt stress, the cutting seedlings were soaked at high salinity (200 mM NaCl) for 0, 4, 12, and 48 h. The seedling leaves and seedling cuttings from both treated and control plants were harvested in the above treatments. For *Pseudomonas syringae* pv. *actinidiae* (Psa) bacterial infection, bacterial cells were suspended in distilled water and adjusted to an OD<sup>600</sup> = 0.2, and injected into the seedling stems, which were carved with a knife. Only carved seedling stems were used as the control (CK), inoculated with Psa, and sampled at 24, 48, and 96 h. Every treated sample had a corresponding regularly-watered control. Three biological replicates were collected per time point, each comprising five independent plants. All samples were immediately frozen in liquid nitrogen and stored at −80 ◦C.
