Dodder is a holoparasitic flowering plant that re-establishes parasitism with the host when broken off from the host. However, how in vitro dodder shoots recycle stored nutrients to maintain growth for reparasitizing hosts is not well characterized. Here, the spatial and temporal distribution characteristics of carbohydrates and reactive oxygen species (ROS) were analysed to explore the mechanism of recycling stored nutrients in dodder shoots in vitro. Our results showed that in vitro dodder shoots grew actively for more than 10 d, while dry mass decreased continuously. During this process, the transcript levels and activities of amylases gradually increased until 2 d and then declined in basal stems, which induced starch degradation at the tissue, cellular and subcellular levels. Additionally, the distribution characteristics of H2O2 and the activities and transcript levels of antioxidant enzymes indicated that shoot tips exhibited more robust ROS-scavenging capacity, and basal stems maintained higher ROS accumulation. Comparative proteomics analysis revealed that starch in basal stems acted as an energy source, and the glycolysis, TCA cycle and pentose phosphate pathway represented the energy supply for shoot tip elongation with time. These results indicated that efficient nutrient recycling and ROS modulation facilitated the parasitism of dodder grown in vitro by promoting shoot elongation growth to reach the host.

中文翻译：

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参与体外寄生植物菟丝子 (Cuscuta spp.) 伸长的抗氧化剂的有效碳循环和调节

菟丝子是一种全寄生开花植物，当与宿主分离时，它会重新建立与宿主的寄生关系。然而，体外菟丝子芽如何回收储存的营养物质以维持再寄生宿主的生长还没有得到很好的描述。在此，通过分析碳水化合物和活性氧 (ROS) 的时空分布特征，探索体外回收菟丝子枝条中储存养分的机制。我们的结果表明，菟丝子的离体枝条生长活跃超过10 d，而干重则不断减少。在这个过程中，淀粉酶的转录水平和活性逐渐增加，直到2 d，然后在基部茎中下降，从而在组织、细胞和亚细胞水平上诱导淀粉降解。此外，H2O2 的分布特征和抗氧化酶的活性和转录水平表明，茎尖表现出更强的 ROS 清除能力，基部茎保持较高的 ROS 积累。比较蛋白质组学分析表明，基部茎中的淀粉作为能量来源，糖酵解、三羧酸循环和磷酸戊糖途径代表了茎尖随时间伸长的能量供应。这些结果表明，有效的养分循环和 ROS 调节通过促进枝条伸长生长到达宿主促进了体外生长的菟丝子的寄生。比较蛋白质组学分析表明，基部茎中的淀粉作为能量来源，糖酵解、三羧酸循环和磷酸戊糖途径代表了茎尖随时间伸长的能量供应。这些结果表明，有效的养分循环和 ROS 调节通过促进枝条伸长生长到达宿主促进了体外生长的菟丝子的寄生。比较蛋白质组学分析表明，基部茎中的淀粉作为能量来源，糖酵解、三羧酸循环和磷酸戊糖途径代表了茎尖随时间伸长的能量供应。这些结果表明，有效的养分循环和 ROS 调节通过促进枝条伸长生长到达宿主促进了体外生长的菟丝子的寄生。