Phenylpropanoids are a class of plant natural products that have many biological functions, including stress defence. In barley, phenylpropanoids have been described as having protective properties against excess UV-B radiation and have been linked to resistance to pathogens. Although the phenylpropanoid composition of barley has recently been addressed in more detail, the biosynthesis and regulation of this pathway have not been fully established. Barley introgression lines, such as the S42IL-population offer a set of genetically diverse plants that enable the correlation of metabolic data to distinct genetic regions on the barley genome and, subsequently, identification of relevant genes. The phenylpropanoid profiles of the first and third leaf of barley seedlings in Scarlett and four members of the S42IL-population were obtained by LC-MS. Comparison of the leaf profiles revealed a change in the glycosylation pattern of the flavone-6-C-glucoside isovitexin in the elite cultivar Scarlett. The change was characterized by the stepwise decrease in isovitexin-7-O-glucoside (saponarin) and an increase in isovitexin-2″-O-β-D-glucoside content. The lines S42IL-101-, -177 and -178 were completely devoid of isovitexin-2″-O-β-D-glucoside. Parallel glucosyltransferase assays were consistent with the observed metabolic patterns. The genetic region responsible for this metabolic effect was located on chromosome 1H between 0.21 and 15.08 cM, encompassing 505 gene candidates in the genome of the sequenced cultivar Morex. Only one of these genes displayed sequence similarity with glucosyltransferases of plant secondary metabolism that possessed the characteristic PSPG motif.

中文翻译：

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大麦幼苗发育过程中isovitexin-O-糖基化的变化

Phenylpropanoids 是一类具有许多生物学功能的植物天然产物，包括应激防御。在大麦中，苯丙烷类化合物被描述为具有防止过量 UV-B 辐射的保护特性，并与对病原体的抵抗力有关。尽管最近更详细地讨论了大麦的苯丙烷类成分，但该途径的生物合成和调节尚未完全确定。大麦基因渗入品系，例如 S42IL 种群，提供了一组遗传多样性植物，可以将代谢数据与大麦基因组上的不同遗传区域相关联，并随后识别相关基因。通过 LC-MS 获得 Scarlett 大麦幼苗第一片和第三片叶以及 S42IL 种群的四个成员的苯丙烷图谱。叶谱的比较揭示了优良品种 Scarlett 中黄酮-6-C-葡萄糖苷异卵黄素的糖基化模式发生了变化。这种变化的特点是isovitexin-7-O-葡萄糖苷（皂苷）的逐步减少和isovitexin-2″-O-β-D-葡萄糖苷含量的增加。品系 S42IL-101-、-177 和 -178 完全不含异卵磷脂-2″-O-β-D-葡萄糖苷。平行的葡萄糖基转移酶测定与观察到的代谢模式一致。负责这种代谢作用的遗传区域位于染色体 1H 上 0.21 至 15.08 cM 之间，包括已测序栽培品种 Morex 基因组中的 505 个候选基因。这些基因中只有一个显示出与具有特征性 PSPG 基序的植物次生代谢的葡糖基转移酶的序列相似性。