In plants, CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) is a key negative regulator in photoperiod response. However, the biological function of COP1-interacting protein 1 (CIP1) and the regulatory mechanism of the CIP1-COP1 interaction are not fully understood. Here, we identified the apple MdCIP1 gene based on the Arabidopsis AtCIP1 gene. Expression pattern analysis showed that MdCIP1 was constitutively expressed in various tissues of apple, and responded to stress and hormone signals at the transcriptional level. Ectopic expression of MdCIP1 complemented the phenotypes of the Arabidopsis cip1 mutant, and MdCIP1 inhibited anthocyanin biosynthesis in apple calli. In addition, the biochemical assay demonstrated that MdCIP1 could interact with MdCOP1 protein by their coiled-coil domain, and MdCIP1-OX/cop1–4 had a similar phenotype in photomorphogenesis with the cop1–4 mutant, suggesting that COP1 is epistatic to CIP1. Furthermore, the transient transformation assay indicated that MdCIP1 repressed anthocyanin biosynthesis in an MdCOP1-mediated pathway. Take together, this study finds that MdCIP1 acts as a repressor in regulating hypocotyl elongation and anthocyanin biosynthesis through MdCOP1 in apple.

中文翻译：

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苹果 MdCOP1 相互作用蛋白 1 负调控下胚轴伸长和花青素生物合成

在植物中，CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) 是光周期响应的关键负调节因子。然而，COP1 相互作用蛋白 1 (CIP1) 的生物学功能和 CIP1-COP1 相互作用的调节机制尚不完全清楚。在这里，我们基于拟南芥 AtCIP1 基因鉴定了苹果 MdCIP1 基因。表达模式分析表明，MdCIP1在苹果的各种组织中组成型表达，并在转录水平对胁迫和激素信号作出反应。MdCIP1 的异位表达补充了拟南芥 cip1 突变体的表型，并且 MdCIP1 抑制了苹果愈伤组织中花青素的生物合成。此外，生化分析表明 MdCIP1 可以通过其卷曲螺旋结构域与 MdCOP1 蛋白相互作用，和 MdCIP1-OX/cop1-4 在光形态发生方面与 cop1-4 突变体具有相似的表型，表明 COP1 对 CIP1 是上位的。此外，瞬时转化试验表明 MdCIP1 抑制了 MdCOP1 介导的途径中的花青素生物合成。综上所述，本研究发现 MdCIP1 在苹果中通过 MdCOP1 调控下胚轴伸长和花青素生物合成的抑制因子。