Japanese plums exhibit wide diversity of fruit coloration. The red to black hues are caused by the accumulation of anthocyanins, while their absence results in yellow, orange or green fruits. In Prunus, MYB10 genes are determinants for anthocyanin accumulation. In peach, QTLs for red plant organ traits map in an LG3 region with three MYB10 copies (PpMYB10.1, PpMYB10.2 and PpMYB10.3). In Japanese plum the gene copy number in this region differs with respect to peach: there are at least three copies of PsMYB10.1, with the expression of one of them (PsMYB10.1a) correlating with fruit skin color. The objective of this study was to determine a possible role of LG3-PsMYB10 genes in the natural variability of the flesh color trait and to develop a molecular marker for marker-assisted selection (MAS). We explored the variability within the LG3-PsMYB10 region using long-range sequences obtained in previous studies through CRISPR-Cas9 enrichment sequencing. We found that the PsMYB10.2 gene was only expressed in red flesh fruits. Its role in promoting anthocyanin biosynthesis was validated by transient overexpression in Japanese plum fruits. The analysis of long-range sequences identified an LTR retrotransposon in the promoter of the expressed PsMYB10.2 gene that explained the trait in 93.1% of the 145 individuals analyzed. We hypothesize that the LTR retrotransposon may promote the PsMYB10.2 expression and activate the anthocyanin biosynthesis pathway. We propose for the first time the PsMYB10.2 gene as candidate for the flesh color natural variation in Japanese plum and provide a molecular marker for MAS.

中文翻译：

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PsMYB10.2 基因启动子中的 LTR 反转录转座子与日本李子果肉颜色的调控相关

日本李子呈现出多种多样的果实颜色。红色到黑色的色调是由花青素的积累引起的，而花青素的缺乏会导致黄色、橙色或绿色的果实。在李属植物中，MYB10 基因是花青素积累的决定因素。在桃中，红色植物器官性状的 QTL 在具有三个 MYB10 拷贝（PpMYB10.1、PpMYB10.2 和 PpMYB10.3）的 LG3 区域作图。在日本李子中，该区域的基因拷贝数与桃子不同：至少有三个 PsMYB10.1 拷贝，其中一个 (PsMYB10.1a) 的表达与果皮颜色相关。本研究的目的是确定 LG3-PsMYB10 基因在肉色性状自然变异中的可能作用，并开发用于标记辅助选择 (MAS) 的分子标记。我们使用先前研究中通过 CRISPR-Cas9 富集测序获得的远程序列探索了 LG3-PsMYB10 区域内的变异性。我们发现PsMYB10.2基因只在红肉果实中表达。它在促进花青素生物合成中的作用已通过在日本李子果实中的瞬时过表达得到验证。对长程序列的分析在表达的 PsMYB10.2 基因的启动子中发现了一个 LTR 反转录转座子，该基因解释了所分析的 145 个个体中 93.1% 的特征。我们假设 LTR 反转录转座子可能促进 PsMYB10.2 表达并激活花青素生物合成途径。我们首次提出 PsMYB10.2 基因作为日本李肉色自然变异的候选基因，并为 MAS 提供了分子标记。