Tamura Yoshio, Mori Tetsuya, Nakabayashi Ryo, Kobayashi Makoto, Saito Kazuki, Okazaki Seiichi, Wang Ning, Kusano Miyako
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
Central Research Institute for Feed and Livestock, National Federation of Agricultural Co-operative Associations, Tsukuba, Japan.
Front Plant Sci. 2018 Jun 27;9:665. doi: 10.3389/fpls.2018.00665. eCollection 2018.
Vegetables produce metabolites that affect their taste and nutritional value and compounds that contribute to human health. The quality of vegetables grown in plant factories under hydroponic cultivation, e.g., their sweetness and softness, can be improved by controlling growth factors including the temperature, humidity, light source, and fertilizer. However, soil is cheaper than hydroponic cultivation and the visual phenotype of vegetables grown under the two conditions is different. As it is not clear whether their metabolite composition is also different, we studied leaf lettuce raised under the hydroponic condition in practical plant factory and strictly controlled soil condition. We chose two representative cultivars, "black rose" (BR) and "red fire" (RF) because they are of high economic value. Metabolite profiling by comprehensive gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) resulted in the annotation of 101 metabolites from 223 peaks detected by GC-MS; LC-MS yielded 95 peaks. The principal component analysis (PCA) scatter plot showed that the most distinct separation patterns on the first principal component (PC1) coincided with differences in the cultivation methods. There were no clear separations related to cultivar differences in the plot. PC1 loading revealed the discriminant metabolites for each cultivation method. The level of amino acids such as lysine, phenylalanine, tryptophan, and valine was significantly increased in hydroponically grown leaf lettuce, while soil-cultivation derived leaf lettuce samples contained significantly higher levels of fatty-acid derived alcohols (tetracosanol and hexacosanol) and lettuce-specific sesquiterpene lactones (lactucopicrin-15-oxalate and 15-deoxylactucin-8-sulfate). These findings suggest that the metabolite composition of leaf lettuce is primarily affected by its cultivation condition. As the discriminant metabolites reveal important factors that contribute to the nutritional value and taste characteristics of leaf lettuce, we performed comprehensive metabolite profiling to identify metabolite compositions, i.e., metabolite signature, that directly improve its quality and value.
蔬菜会产生影响其口感和营养价值的代谢产物以及对人体健康有益的化合物。在水培条件下于植物工厂种植的蔬菜，例如其甜度和柔软度，可以通过控制包括温度、湿度、光源和肥料在内的生长因素来改善。然而，土壤比水培种植成本更低，且在这两种条件下种植的蔬菜外观表型有所不同。由于尚不清楚它们的代谢产物组成是否也存在差异，我们研究了在实际植物工厂水培条件下种植且严格控制土壤条件的生菜。我们选择了两个具有代表性的品种，“黑玫瑰”（BR）和“红火焰”（RF），因为它们具有较高的经济价值。通过综合气相色谱 - 质谱联用（GC - MS）和液相色谱 - 质谱联用（LC - MS）进行代谢物谱分析，从GC - MS检测到的223个峰中鉴定出101种代谢物；LC - MS产生了95个峰。主成分分析（PCA）散点图显示，在第一主成分（PC1）上最明显的分离模式与种植方法的差异一致。图中没有与品种差异相关的明显分离。PC1载荷揭示了每种种植方法的判别代谢物。水培生菜中赖氨酸、苯丙氨酸、色氨酸和缬氨酸等氨基酸水平显著升高，而土壤栽培的生菜样品中脂肪酸衍生醇（二十四醇和二十六醇）以及生菜特有的倍半萜内酯（15 - 草酸莴苣苦素和15 - 脱氧莴苣素 - 8 - 硫酸盐）水平显著更高。这些发现表明生菜的代谢物组成主要受其种植条件影响。由于判别代谢物揭示了影响生菜营养价值和口感特征的重要因素，我们进行了全面的代谢物谱分析以确定直接改善其品质和价值的代谢物组成，即代谢物特征。
