As an important environment factor, light affects plant growth and development throughout life. B-BOX (BBX) proteins play key roles in the regulation of light signaling. Although the multiple roles of BBX proteins have been extensively studied in Arabidopsis, the research in apple is much less extensive. In this study, we systematically characterized the negative role of an apple BBX protein MdBBX37 in light signaling, including inhibiting anthocyanin biosynthesis and promoting hypocotyl elongation. We found that MdBBX37 interacted with MdMYB1 and MdMYB9, two key positive regulators of anthocyanin biosynthesis, and inhibited the binding of those two proteins to their target genes and, therefore, negatively regulated anthocyanin biosynthesis. In addition, MdBBX37 directly bound to the promoter of MdHY5, a positive regulator of light signaling, and suppressed its expression, and thus relieved MdHY5-mediated hypocotyl inhibition. Taken together, our investigations suggest that MdBBX37 is a negative regulator of light signaling in apple. Our study will provide reference for further study on the functions of BBX proteins in apple.

中文翻译：

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苹果B-Box蛋白MdBBX37与MdMYB和MdHY5协同调节花色苷的生物合成和下胚轴伸长。

作为重要的环境因素，光会影响植物的生长和发育。B-BOX（BBX）蛋白在调节光信号中起关键作用。尽管在拟南芥中已经广泛研究了BBX蛋白的多种作用，但在苹果中的研究却远没有那么广泛。在这项研究中，我们系统地表征了苹果BBX蛋白MdBBX37在光信号传导中的负作用，包括抑制花色苷的生物合成和促进下胚轴伸长。我们发现，MdBBX37与花青素生物合成的两个关键正调节剂MdMYB1和MdMYB9相互作用，并且抑制了这两种蛋白与其靶基因的结合，因此对花青素生物合成进行了负调控。此外，MdBBX37直接与MdHY5的启动子结合，MdHY5是光信号的阳性调节子，并抑制其表达，从而减轻MdHY5介导的下胚轴抑制作用。综上所述，我们的研究表明MdBBX37是苹果中光信号的负调节剂。我们的研究将为进一步研究BBX蛋白在苹果中的功能提供参考。