Noni (Morinda citrifolia Linn.) is a tropical tree that bears climacteric fruit. Previous observations and research have shown that the second day (2 d) after harvest is the most important demarcation point when the fruit has the same appearance as the freshly picked fruit (0 d); however, they are beginning to become water spot appearance. We performed a conjoint analysis of metabolome and transcriptome data for noni fruit of 0 d and 2 d to reveal what happened to the fruit at the molecular level. Genes and metabolites were annotated to KEGG pathways and the co-annotated KEGG pathways were used as a statistical analysis. We found 25 pathways that were significantly altered at both metabolic and transcriptional levels, including a total of 285 differentially expressed genes (DEGs) and 11 differential metabolites through an integrative analysis of transcriptomics and metabolomics. The energy metabolism and pathways originating from phenylalanine were disturbed the most. The upregulated resistance metabolites and genes implied the increase of resistance and energy consumption in the postharvest noni fruit. Most genes involved in glycolysis were downregulated, further limiting the available energy. This lack of energy led noni fruit to water spot appearance, a prelude to softening. The metabolites and genes related to the resistance and energy interacted and restricted each other to keep noni fruit seemingly hard within two days after harvest, but actually the softening was already unstoppable. This study provides a new insight into the relationship between the metabolites and genes of noni fruit, as well as a foundation for further clarification of the post-ripening mechanism in noni fruit.

中文翻译：

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诺丽果在收获的第二天出现水斑：阻力与能量之间的权衡

Noni（Morinda citrifolia Linn。）是一棵热带植物，具有更年期的果实。先前的观察和研究表明，当果实与新鲜采摘的果实（0 d）具有相同的外观时，收获后第二天（2 d）是最重要的分界点。但是，它们开始成为水斑。我们对0天和2天诺丽果的代谢组和转录组数据进行了联合分析，以揭示在分子水平上该果发生了什么。将基因和代谢物标注为KEGG途径，并将共同标注的KEGG途径用作统计分析。我们发现了25种在代谢和转录水平上均发生了显着改变的途径，通过转录组学和代谢组学的综合分析，包括总共285个差异表达基因（DEG）和11个差异代谢物。来自苯丙氨酸的能量代谢和途径受干扰最大。抗性代谢物和基因的上调暗示了采后诺丽果抗性和能量消耗的增加。参与糖酵解的大多数基因被下调，进一步限制了可用能量。能量的缺乏导致诺丽果出现水斑，这是软化的前奏。与抗性和能量有关的代谢物和基因相互作用并相互制约，以使诺丽果在收获后两天内看起来很坚硬，但实际上其软化作用已经不可阻挡。