Anthocyanin pigmentation is an important consumption trait of apple (Malus domestica). In this study, we focused on the identification of NAC (NAM, ATAF1/2, and CUC2) proteins involved in the regulation of anthocyanin acuumulation in apple flesh. A group of MdNACs was selected for comparison of expression patterns between the white-fleshed cultivar 'Granny Smith' and red-fleshed 'Redlove'. Among them, MdNAC42 was screened, which exhibited higher expression level in red-fleshed than in white-fleshed, and has positive correlation with anthocyanin content as fruits ripened. Moreover, overexpression of MdNAC42 in apple calli resulted in the up-regulation of flavonoid pathway genes, including MdCHS, MdCHI, MdF3H, MdDFR, MdANS, and MdUFGT, thereby increasing the accumulation of anthocyanins, which confirmed the roles of MdNAC42 in anthocyanin biosynthesis. Notably, MdNAC42 was demonstrated to have an obvious interaction with MdMYB10 either in vitro or in vivo by yeast two-hybrid combined with bimolecular fluorescence complementation, further suggesting that MdNAC42 is an important part of the regulatory network controlling the anthocyanin pigmentation of red-fleshed apples. To the best of our knowledge, this is the first report on identifying MdNAC gene related to anthocyanin accumulation in the red-fleshed apples. This study provided valuable information for improving the regulatory model of anthocyanin biosynthesis in apple fruit.

中文翻译：

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新型NAC转录因子MdNAC42通过与MdMYB10相互作用来调节红肉苹果中的花色苷积累。

花青素色素沉着是苹果（Malus domestica）的重要消费特性。在这项研究中，我们着重于NAC（NAM，ATAF1 / 2和CUC2）蛋白的鉴定，这些蛋白与苹果果肉中花青素累积的调节有关。选择一组MdNAC用于比较白肉品种“格兰尼·史密斯”和红肉品种“ Redlove”之间的表达模式。其中，筛选出MdNAC42，其在红色果肉中表达水平高于在白色果肉中表达水平，并且随着果实成熟而与花色苷含量呈正相关。此外，MdNAC42在苹果愈伤组织中的过表达导致类黄酮途径基因（包括MdCHS，MdCHI，MdF3H，MdDFR，MdANS和MdUFGT）的上调，从而增加了花色苷的积累，这证实了MdNAC42在花青素生物合成中的作用。值得注意的是，通过酵母双杂交结合双分子荧光互补，证明MdNAC42在体外或体内与MdMYB10有明显的相互作用，进一步表明MdNAC42是调控网络中红肉苹果花色苷色素沉着的重要组成部分。 。据我们所知，这是关于鉴定与红肉苹果中花色苷积累有关的MdNAC基因的第一份报告。该研究为改善苹果果实花色苷生物合成调控模型提供了有价值的信息。进一步提示，MdNAC42是控制红肉苹果花色苷色素沉着的调控网络的重要组成部分。据我们所知，这是关于鉴定与红肉苹果中花色苷积累有关的MdNAC基因的第一份报告。该研究为改善苹果果实花色苷生物合成调控模型提供了有价值的信息。进一步提示，MdNAC42是控制红肉苹果花色苷色素沉着的调控网络的重要组成部分。据我们所知，这是关于鉴定与红肉苹果中花色苷积累有关的MdNAC基因的第一份报告。该研究为改善苹果果实花色苷生物合成调控模型提供了有价值的信息。