人参皂苷合成酶PgHMGR1/2调控人参耐旱性的机理研究

Ginseng（Panax ginseng C. A. Meyer）is a perennial herbaceous plant, which has been cultivated for over 2000 years as a medicinal plant for its highly valued roots. Drought is one of the major stresses that affect the growth and yield of ginseng. However, little is known about the responses of ginseng to drought stress. The plant hormone abscisic acid (ABA) has been shown to mediate drought stress responsing a variety of plants including the model plant Arabidopsis. We found that exogenous application of ABA led to enhanced drought tolerance, and accumulation of ginsenosides, important pharmaceutically active components, in ginseng. Most importantly, we found that ABA can induce the expression of PgHMGR1/2, two ginseng genes encoding the ginsenoside biosynthetic enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), and that Arabidopsis HMGR interacts with protein phosphatase type 2C (PP2C) ABI1 (ABA-INSENSITIVE 1), a negative regulator of ABA signaling pathway. These results indicate that PgHMGR1/2 may play a role in ABA mediated drought tolerance in ginseng. To further explore this possibility, a combination of molecular, physiological, biochemical and bioinformatic approaches will be employed to examine the roles of PgHMGR1/2 in drought responses in ginseng, to test if PgHMGR1/2 interacts with ginseng ABI1, and to pinpoint the preciously roles of PgHMGR1/2 in ABA signaling in ginseng. Results obtained from this research will provide new insights into the regulation of ABA signaling in plants other than the model plant Arabidopsis, and directly lead to the genetic improvement of ginseng to make it more tolerance to drought stress.

人参是我国名贵的中药材，干旱胁迫是造成人参减产的主要非生物胁迫之一，但对人参响应干旱胁迫的机制研究较少。植物激素ABA能够介导多种植物对干旱胁迫的响应，我们的初步结果表明，外源ABA处理能够增强人参对干旱胁迫的耐受力，同时也能够促进人参皂苷的积累。尤为重要的是，我们发现ABA能诱导人参皂苷合成酶基因PgHMGR1/2的表达，而PgHMGR1/2在拟南芥中的同源蛋白HMGR2可以和ABA信号转导负调节因子ABI1相互作用。在此基础上，我们将综合利用分子生物学、生物化学及生物信息学等学科的技术和方法，从研究PgHMGR1/2对人参响应干旱胁迫的影响，检测PgHMGR1/2与PgABI1的互作，及PgHMGR1/2对ABA信号转导的影响等方面入手，探究PgHMGR1/2在ABA介导的人参干旱胁迫响应中的作用。研究结果将丰富有关ABA信号转导的理论知识，为有效解决人参的干旱胁迫问题提供科学依据。

人参（Panax ginseng C. A. Meyer）是我国名贵的中药材，人参皂苷是人参中最重要的生理活性物质。目前关于人参皂苷的研究主要集中在对其药理活性进行分析，而对干旱胁迫下人参皂苷的生物合成情况却是目前研究的空白。植物激素ABA（abscisic acid，ABA） 在调控多种植物活性物质合成过程中发挥着重要作用，但其在人参皂苷合成过程中的研究几乎为零。我们的前期的研究结果发现，外源ABA处理不仅能够促进人参皂苷的积累， 还能诱导人参皂苷合成酶基因PgHMGR1/2的表达。而后，我们综合利用分子生物学、生物化学及生物信息学等学科的技术和方法，从分离并鉴定PgHMGR1/2在植物激素ABA信号通路中的靶标分子入手，分离鉴定到在ABA信号通路中，PgHMGR1/2通过和ABA信号通路中的重要的负调控因子ABI1相互作用，参与ABA信号的调控响应干旱胁迫。同时，ABA又通过ABI1与HMGR1/2的相互作用调控了人参皂苷的生物合成。该研究初步探明了PgHMGR1/2通过和ABI1相互作用响应干旱胁迫的机制。研究结果为未来人参的绿色种植，优良品种培育提供了科学依据，为降低以人参皂苷为主要成分的药品及保健品的生产成本提供前期保障，为人参皂苷在未来生活中的普及使用提供理论基础。