State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing, 100085, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Mycorrhiza. 2018 Apr;28(3):285-300. doi: 10.1007/s00572-018-0827-y. Epub 2018 Feb 17.
Liquorice (Glycyrrhiza uralensis) is an important medicinal plant for which there is a huge market demand. It has been reported that arbuscular mycorrhizal (AM) symbiosis and drought stress can stimulate the accumulation of the active ingredients, glycyrrhizin and liquiritin, in liquorice plants, but the potential interactions of AM symbiosis and drought stress remain largely unknown. In the present work, we investigated mycorrhizal effects on plant growth and accumulation of glycyrrhizin and liquiritin in liquorice plants under different water regimes. The results indicated that AM plants generally exhibited better growth and physiological status including stomatal conductance, photosynthesis rate, and water use efficiency compared with non-AM plants. AM inoculation up-regulated the expression of an aquaporin gene PIP and decreased root abscisic acid (ABA) concentrations under drought stress. In general, AM plants displayed lower root carbon (C) and nitrogen (N) concentrations, higher phosphorus (P) concentrations, and therefore, lower C:P and N:P ratios but higher C:N ratio than non-AM plants. On the other hand, AM inoculation increased root glycyrrhizin and liquiritin concentrations, and the mycorrhizal effects were more pronounced under moderate drought stress than under well-watered condition or severe drought stress for glycyrrhizin accumulation. The accumulation of glycyrrhizin and liquiritin in AM plants was consistent with the C:N ratio changes in support of the carbon-nutrient balance hypothesis. Moreover, the glycyrrhizin accumulation was positively correlated with the expression of glycyrrhizin biosynthesis genes SQS1, β-AS, CYP88D6, and CYP72A154. By contrast, no significant interaction of AM inoculation with water treatment was observed for liquiritin accumulation, while we similarly observed a positive correlation between liquiritin accumulation and the expression of a liquiritin biosynthesis gene CHS. These results suggested that AM inoculation in combination with proper water management potentially could improve glycyrrhizin and liquiritin accumulation in liquorice roots and may be practiced to promote liquorice cultivation.
甘草（Glycyrrhiza uralensis）是一种重要的药用植物，市场需求量巨大。据报道，丛枝菌根（AM）共生和干旱胁迫可以刺激甘草植物中活性成分甘草酸和甘草苷的积累，但 AM 共生和干旱胁迫的潜在相互作用在很大程度上仍不清楚。在本工作中，我们研究了 AM 共生对不同水分条件下甘草植物生长和甘草酸、甘草苷积累的影响。结果表明，与非 AM 植物相比，AM 植物通常表现出更好的生长和生理状态，包括气孔导度、光合作用速率和水分利用效率。干旱胁迫下，AM 接种上调了水通道蛋白基因 PIP 的表达，降低了根中脱落酸（ABA）的浓度。一般来说，AM 植物的根碳（C）和氮（N）浓度较低，磷（P）浓度较高，因此 C：P 和 N：P 比值较低，C：N 比值较高，但非 AM 植物则相反。另一方面，AM 接种增加了根中甘草酸和甘草苷的浓度，且在中度干旱胁迫下，与水分充足或重度干旱胁迫相比，AM 对甘草酸积累的影响更为显著。AM 接种对甘草酸和甘草苷积累的影响与根中 C：N 比的变化一致，支持碳-养分平衡假说。此外，甘草酸积累与甘草酸生物合成基因 SQS1、β-AS、CYP88D6 和 CYP72A154 的表达呈正相关。相比之下，AM 接种与水分处理之间没有明显的相互作用，我们也观察到了甘草苷积累与 CHS 基因表达的正相关。这些结果表明，AM 接种与适当的水分管理相结合，可能会提高甘草根中甘草酸和甘草苷的积累，并可能用于促进甘草的种植。
