Tomato is an important economic crop all over the world. Volatile flavors in tomato fruit are key factors influencing consumer liking and commercial quality. However, the regulatory mechanism controlling the volatile flavors of tomatoes is still not clear. Here, we integrated the metabolome and transcriptome of the volatile flavors in tomato fruit to explore the regulatory mechanism of volatile flavor formation, using wild and cultivated tomatoes with significant differences in flavors. A total of 35 volatile flavor compounds were identified, based on the solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The content of the volatiles, affecting fruit flavor, significantly increased in the transition from breaker to red ripe fruit stage. Moreover, the total content of the volatiles in wild tomatoes was much higher than that in the cultivated tomatoes. The content variations of all volatile flavors were clustered into 10 groups by hierarchical cluster and Pearson coefficient correlation (PCC) analysis. The fruit transcriptome was also patterned into 10 groups, with significant variations both from the mature green to breaker fruit stage and from the breaker to red ripe fruit stage. Combining the metabolome and the transcriptome of the same developmental stage of fruits by co-expression analysis, we found that the expression level of 1 182 genes was highly correlated with the content of volatile flavor compounds, thereby constructing two regulatory pathways of important volatile flavors. One pathway is tetrahydrothiazolidine N-hydroxylase (SlTNH1)-dependent, which is regulated by two transcription factors (TFs) from the bHLH and AP2/ERF families, controlling the synthesis of 2-isobutylthiazole in amino acid metabolism. The other is lipoxygenase (SlLOX)-dependent, which is regulated by one TF from the HD-Zip family, controlling the synthesis of hexanal and (Z)-2-heptenal in fatty acid metabolism. Dual-luciferase assay confirmed the binding of bHLH and AP2/ERF to their structural genes. The findings of this study provide new insights into volatile flavor formation in tomato fruit, which can be useful for tomato flavor improvement.

中文翻译：

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转录组和代谢组的整合揭示了番茄果实成熟过程中挥发性风味形成的调控机制


西红柿是全世界重要的经济作物。番茄果实中挥发的风味是影响消费者喜好和商业质量的关键因素。然而，控制西红柿挥发性风味的调节机制仍不清楚。在这里，我们整合了番茄果实中挥发性风味的代谢组和转录组，以风味差异显著的野生和栽培番茄为研究对象，探索挥发性风味形成的调控机制。基于固相微萃取-气相色谱-质谱 （SPME-GC-MS） 共鉴定出 35 种挥发性风味化合物。影响果实风味的挥发物含量在从破果期到红熟果期的过渡中显著增加。此外，野生西红柿中挥发物的总含量远高于栽培西红柿。通过分层聚类和 Pearson 系数相关 （PCC） 分析将所有挥发性风味的含量变化分为 10 组。果实转录组也被分为 10 组，从成熟的绿色到破果期和从破果期到红色成熟果期都有显著差异。将水果同一发育阶段的代谢组和转录组通过共表达分析，发现 1 182 个基因的表达水平与挥发性风味物质含量高度相关，从而构建了重要挥发性风味的两条调控途径。一种途径是四氢噻唑烷 N-羟化酶 （SlTNH1） 依赖性通路，受来自 bHLH 和 AP2/ERF 家族的两个转录因子 （TF） 的调节，控制氨基酸代谢中 2-异丁基噻唑的合成。 另一种是脂氧合酶 （SlLOX） 依赖性，它由 HD-Zip 家族的一个 TF 调节，控制脂肪酸代谢中己醛和 （Z）-2-庚烯醛的合成。双荧光素酶测定证实了 bHLH 和 AP2/ERF 与其结构基因的结合。本研究结果为番茄果实中挥发性风味的形成提供了新的见解，可用于改善番茄风味。