The phytohormone abscisic acid (ABA) regulates plant growth and development and stress resistance through the ABA receptor PYLs. To date, no interaction between CPK and PYL has been reported, even in Arabidopsis and rice. In this study, we found that MdCPK4 from Malus domestica (Md for short) interacts with two MdPYLs, MdPYL2/12, in the nucleus and the cytoplasm in vivo and phosphorylates the latter in vitro as well. Compared with the wild type (WT), the MdCPK4- or MdPYL2/12-overexpressing Arabidopsis lines showed more sensitivity to ABA, and therefore stronger drought resistance. The ABA-related genes (ABF1, ABF2, ABF4, RD29A and SnRK2.2) were significantly upregulated in the overexpressing (OE) lines after ABA treatment. These results indicate that MdCPK4 and MdPYL2/12 act as positive regulators in response to ABA-mediated drought resistance in apple. Our results reveal the relationship between MdCPK4 and MdPYL2/12 in ABA signaling, which will further enrich the molecular mechanism of drought resistance in plants.

植物激素脱落酸(ABA) 通过 ABA 受体 PYL 调节植物的生长发育和抗逆性。迄今为止，即使在拟南芥和水稻中，也没有报道 CPK 和 PYL 之间的相互作用。在本研究中，我们发现来自Malus Domestica（简称Md）的MdCPK4在体内与细胞核和细胞质中的两个MdPYL（MdPYL2/12）相互作用，并在体外磷酸化后者。与野生型（WT）相比，过表达MdCPK4或MdPYL2/12的拟南芥品系对ABA更加敏感，因此具有更强的抗旱性。ABA 处理后，过表达（OE）系中ABA 相关基因（ABF1、ABF2、ABF4、RD29A和SnRK2.2 ）显着上调。这些结果表明，MdCPK4 和 MdPYL2/12 作为苹果响应 ABA 介导的抗旱性的正调节因子。我们的研究结果揭示了MdCPK4和MdPYL2/12在ABA信号传导中的关系，这将进一步丰富植物抗旱的分子机制。