Melon fruit flavor is a key quality characteristic that influences consumer preference. Grafting is an effective technique to enhance fruit quality but yields divergent outcomes in terms of fruit flavor. To address this problem, we analyzed parallel changes in flavor-related metabolite accumulation and gene expression in two pumpkin rootstock grafted melons during four fruit developmental stages. We identified 26 061 expressed genes and 840 metabolites from 21 different compound classes, including carbohydrates, amino acids, and lipids. We also detected 50 aroma volatile compounds in the grafted melons. Results showed that genes and metabolites associated with metabolic pathways (carbohydrate, amino acid, lipid, and phenylpropanoid) play a key role in flavor formation. Compared with ‘Sizhuang 12’, ‘Tianzhen 1’ rootstock improved melon fruit flavor by upregulating sugar-related genes (, , , and ) and inducing metabolite accumulation (-ribose-5-phosphate, -galactose, and trehalose 6-phosphate), whereas decreasing bitterness-related amino acids (-arginine, -asparagine, and -tyrosine) and associated genes (, , and ) expression at ripening stage. Furthermore, ‘Tianzhen 1’ exhibited higher expression levels of enzyme-coding genes (, , ) responsible for aroma volatile synthesis than ‘Sizhuang 12’ rootstock. Taken together, our results decipher the basis of the molecular mechanism underlying fruit flavor in grafted melons and provide valuable information for the melons genetic improvement.

中文翻译：

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综合多组学分析提供了对嫁接到两种不同南瓜砧木上的甜瓜在果实发育过程中风味变化的分子见解


瓜果风味是影响消费者偏好的关键质量特性。嫁接是提高果实品质的有效技术，但在果实风味方面产生不同的结果。为了解决这个问题，我们分析了两个南瓜砧木嫁接甜瓜在四个果实发育阶段的风味相关代谢物积累和基因表达的平行变化。我们从 21 种不同的化合物类别（包括碳水化合物、氨基酸和脂质）中鉴定出 26 061 个表达基因和 840 种代谢物。我们还在嫁接瓜中检测出了50种香气挥发性化合物。结果表明，与代谢途径相关的基因和代谢物（碳水化合物、氨基酸、脂质和苯丙素）在风味形成中发挥着关键作用。与‘四庄12号’相比，‘天珍1号’砧木通过上调糖相关基因（、、、和）和诱导代谢物积累（-核糖-5-磷酸、-半乳糖和海藻糖6-磷酸）来改善瓜果风味，而在成熟阶段降低与苦味相关的氨基酸（-精氨酸、-天冬酰胺和-酪氨酸）和相关基因（、、和）的表达。此外，‘天珍1号’负责香气挥发物合成的酶编码基因(, , )的表达水平高于‘四庄12号’砧木。总而言之，我们的结果破译了嫁接甜瓜果味的分子机制基础，并为甜瓜遗传改良提供了有价值的信息。