The functions of l-isoleucine (Ile) in anthocyanin biosynthesis were investigated in apple fruit. Whole trees (Malus × domestica Bokh.) were treated with Ile or n-propyl dihydrojasmonate (PDJ), which is a jasmonic acid (JA) analog, 20 and 30 days before harvest. Both Ile and PDJ treatments stimulated anthocyanin formation at 30 and 35 days after treatment (DAT). The expressions of MdUF3GT and MdMYB1 genes under the Ile and PDJ treatments were higher than those in the untreated control at 19 and 30 DAT. Endogenous JA and jasmonoyl-l-isoleucine (JA-Ile) concentrations in Ile- and PDJ- treated fruit were increased at 19 and 30 DAT. At 30 DAT, the Ile and PDJ treatments stimulated the expressions of MdJAR1, which is related to the conjugation of JA to Ile, and MdMYC2, which is a transcription factor in the JA response. Our study suggests that Ile can induce anthocyanin formation depending on the increase of JA-Ile production and the up-regulation of MdJAR1 and MdMYC2 in apples.

中文翻译：

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l-异亮氨酸（Ile）促进苹果中花青素的积累

在苹果果实中研究了 l-异亮氨酸 (Ile) 在花青素生物合成中的作用。在收获前 20 天和 30 天，用 Ile 或正丙基二氢茉莉酮酸酯 (PDJ)（一种茉莉酸 (JA) 类似物）处理整棵树（Malus ×domestica Bokh.）。Ile 和 PDJ 处理均在处理后 30 天和 35 天 (DAT) 刺激了花青素的形成。在 Ile 和 PDJ 处理下，MdUF3GT 和 MdMYB1 基因的表达在 19 天和 30 天高于未处理的对照。在 Ile 和 PDJ 处理的果实中，内源性 JA 和茉莉酰-l-异亮氨酸 (JA-Ile) 浓度在 19 天和 30 天增加。在 30 DAT，Ile 和 PDJ 处理刺激了 MdJAR1 的表达，这与 JA 与 Ile 的结合有关，以及 MdMYC2 的表达，MdMYC2 是 JA 反应中的转录因子。