Santin Marco, Castagna Antonella, Miras-Moreno Begoña, Rocchetti Gabriele, Lucini Luigi, Hauser Marie-Theres, Ranieri Annamaria
Department of Agriculture, Food and Environment, University of Pisa, Pisa, Italy.
Interdepartmental Research Center Nutrafood "Nutraceuticals and Food for Health", University of Pisa, Pisa, Italy.
Front Plant Sci. 2020 Oct 30;11:579063. doi: 10.3389/fpls.2020.579063. eCollection 2020.
In the last decades, UV-B radiation has attracted attention due to its potential to increase nutraceutical values of fruit and vegetables, especially by inducing the accumulation of phenolics in a structure-dependent way. However, most current studies have investigated the UV-B-driven changes only in the peel or focusing on individual phenolic classes. Adopting an "-omics" approach, this work aimed to deepen the knowledge about the effects of UV-B radiation on the phenolic profile in the pulp of peach fruit. Based on these considerations, melting flesh yellow peaches ( L., cv. Fairtime) were subjected to either a 10- or 60-min UV-B treatment (1.39 and 8.33 kJ m, respectively), and sampled at different time points from the exposure. A UHPLC-ESI/QTOF-MS analysis coupled with a phenolics-specific database for the annotation of compounds and a multivariate discriminant analysis revealed a marked effect of UV-B radiation on the phenolic profiles of peach pulp. Particularly, a general, transient increase was observed after 24 h from the irradiation, especially for flavanols, flavonols, and flavones. Such behavior diverges from what was observed in the peel, where an overall increase of phenolics was observed after 36 h from the irradiation. Concerning the flavonols in the pulp, UV-B exposure stimulated a specific accumulation of isorhamnetin and kaempferol derivatives, with variations imposed by the different sugar moiety bound. Anthocyanins, which were the second most abundant flavonoid group after flavonols, displayed a general decrease after 36 h that was not attributable to specific molecules. The UV-B treatments also increased the glycoside/aglycone ratio of flavonols and anthocyanins after 24 h, by increasing the glycoside concentration of both, flavonols and anthocyanins, and decreasing the aglycone concentration of anthocyanins. In support of the biochemical results, targeted gene expression analysis by RT-qPCR revealed an UV-B-induced activation of many genes involved in the flavonoid pathway, e.g., CHS, F3H, F3'H, DFR, as well as some MYB transcription factors and few genes involved in the UV-B perception. Generally, all the flavonoid-related and MYB genes showed a transient UV-B dose-dependent activation after 6 h from the irradiation, similarly to what was observed in the peel.
在过去几十年中，UV-B辐射因其有可能提高水果和蔬菜的营养保健价值而受到关注，特别是它能以结构依赖的方式诱导酚类物质的积累。然而，目前大多数研究仅调查了UV-B辐射对果皮的影响，或仅关注个别酚类物质类别。本研究采用“组学”方法，旨在深入了解UV-B辐射对桃果肉中酚类物质谱的影响。基于这些考虑，对溶质型黄肉桃（L.，品种Fairtime）进行了10分钟或60分钟的UV-B处理（分别为1.39和8.33 kJ m²），并在照射后的不同时间点取样。通过超高效液相色谱-电喷雾电离/四极杆飞行时间质谱（UHPLC-ESI/QTOF-MS）分析，结合用于化合物注释的酚类物质特异性数据库和多变量判别分析，揭示了UV-B辐射对桃果肉酚类物质谱有显著影响。特别是，照射后24小时观察到普遍的、短暂的增加，尤其是黄烷醇、黄酮醇和黄酮。这种行为与在果皮中观察到的情况不同，在果皮中，照射后36小时观察到酚类物质总体增加。关于果肉中的黄酮醇，UV-B照射刺激了异鼠李素和山奈酚衍生物的特异性积累，其变化受结合的不同糖部分的影响。花青素是仅次于黄酮醇的第二丰富的黄酮类化合物组，在36小时后总体呈下降趋势，这并非归因于特定分子。UV-B处理还在24小时后提高了黄酮醇和花青素的糖苷/苷元比，这是通过增加黄酮醇和花青素两者的糖苷浓度以及降低花青素的苷元浓度实现的。为支持生化结果，通过逆转录定量聚合酶链反应（RT-qPCR）进行的靶向基因表达分析显示，UV-B诱导了许多参与类黄酮途径的基因的激活，例如查尔酮合酶（CHS）、黄烷酮3-羟化酶（F3H）、黄酮醇3'-羟化酶（F3'H）、二氢黄酮醇4-还原酶（DFR），以及一些MYB转录因子和少数参与UV-B感知的基因。一般来说，所有与类黄酮相关的基因和MYB基因在照射后6小时显示出短暂的UV-B剂量依赖性激活，这与在果皮中观察到的情况类似。
