Lycopene content in tomato fruit is largely under genetic control and varies greatly among genotypes. Continued improvement of lycopene content in elite varieties with conventional breeding has become challenging, in part because little is known about the underlying molecular mechanisms in high-lycopene tomatoes (HLYs). We collected 42 HLYs with different genetic backgrounds worldwide. High-performance liquid chromatography (HPLC) analysis revealed lycopene contents differed among the positive control wild tomato Solanum pimpinellifolium, HLYs, the normal lycopene cultivar “Moneymaker”, and the non-lycopene cultivar NC 1Y at the pink and red ripe stages. Real-time RT-PCR analysis of expression of the 25 carotenoid biosynthesis pathway genes of each genotype showed a significantly higher expression in nine upstream genes (GGPPS1, GGPPS2, GGPPS3, TPT1, SSU II, PSY2, ZDS, CrtISO and CrtISO-L1 but not the well-studied PSY1, PDS and Z-ISO) at the breaker and/or red ripe stages in HLYs compared to Moneymaker, indicating a higher metabolic flux flow into carotenoid biosynthesis pathway in HLYs. Further conversion of lycopene to carotenes may be prevented via the two downstream genes (β-LCY2 and ε-LCY), which had low-abundance transcripts at either or both stages. Additionally, the significantly higher expression of four downstream genes (BCH1, ZEP, VDE, and CYP97C11) at either or both ripeness stages leads to significantly lower fruit lycopene content in HLYs than in the wild tomato. This is the first systematic investigation of the role of the complete pathway genes in regulating fruit lycopene biosynthesis across many HLYs, and enables tomato breeding and gene editing for increased fruit lycopene content.

中文翻译：

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类胡萝卜素生物合成的协调转录调控有助于高番茄红素番茄基因型中的番茄红素含量

番茄果实中的番茄红素含量主要受遗传控制，并且在不同基因型之间差异很大。通过常规育种持续提高优良品种的番茄红素含量变得具有挑战性，部分原因是人们对高番茄红素番茄 (HLYs) 的潜在分子机制知之甚少。我们在全球范围内收集了 42 个具有不同遗传背景的 HLY。高效液相色谱 (HPLC) 分析显示，阳性对照野生番茄 Solanum pimpinellifolium、HLYs、正常番茄红素品种“Moneymaker”和非番茄红素品种 NC 1Y 在粉红色和红色成熟阶段的番茄红素含量存在差异。对每种基因型的 25 个类胡萝卜素生物合成途径基因的表达进行实时 RT-PCR 分析显示，9 个上游基因（GGPPS1、GGPPS2、GGPPS3、与 Moneymaker 相比，HLYs 的破发期和/或红熟期的 TPT1、SSU II、PSY2、ZDS、CrtISO 和 CrtISO-L1（但不是经过充分研究的 PSY1、PDS 和 Z-ISO），表明流入的代谢通量更高HLYs中的类胡萝卜素生物合成途径。可以通过两个下游基因（β-LCY2 和 ε-LCY）阻止番茄红素进一步转化为胡萝卜素，这两个基因在任一或两个阶段都具有低丰度转录物。此外，四个下游基因（BCH1、ZEP、VDE 和 CYP97C11）在任一成熟阶段或两个成熟阶段的显着较高表达导致 HLYs 中的果实番茄红素含量显着低于野生番茄。这是第一次系统研究完整途径基因在调节许多 HLY 的果实番茄红素生物合成中的作用，