Drought stress is a severe source of abiotic stress that can affect apple yield and quality, yet the underlying molecular mechanism of the drought stress response and the role of MdBT2 in the process remain unclear. Here, we find that MdBT2 negatively regulates the drought stress response. Both in vivo and in vitro assays indicated that MdBT2 interacted physically with and ubiquitinated MdNAC143, a member of the NAC TF family that is a positive regulator under drought stress. In addition, MdBT2 promotes the degradation of MdNAC143 via the 26S proteasome system. A series of transgenic assays in apple calli and Arabidopsis verify that MdBT2 confers susceptibility to drought stress at least in part by the regulation of MdNAC143. Overall, our findings provide new insight into the mechanism of MdBT2, which functions antagonistically to MdNAC143 in regulating drought stress by regulating the potential downstream target protein MdNAC143 for proteasomal degradation in apple.

中文翻译：

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BTB-TAZ 蛋白 MdBT2 通过与苹果中的转录因子 MdNAC143 相互作用负向调节干旱应激反应

干旱胁迫是影响苹果产量和品质的非生物胁迫的严重来源，但干旱胁迫响应的潜在分子机制和 MdBT2 在该过程中的作用仍不清楚。在这里，我们发现 MdBT2 负向调节干旱胁迫反应。体内和体外测定均表明 MdBT2 与 MdNAC143 发生物理相互作用并泛素化，MdNAC143 是 NAC TF 家族的成员，是干旱胁迫下的正调节因子。此外，MdBT2 通过 26S 蛋白酶体系统促进 MdNAC143 的降解。苹果愈伤组织和拟南芥中的一系列转基因试验证实 MdBT2 至少部分通过 MdNAC143 的调节赋予对干旱胁迫的易感性。总的来说，我们的发现为 MdBT2 的机制提供了新的见解，