人参皂苷对人参根际真菌选择性促抑的分子机制

During the planting process, Panax ginseng is attacked by a diverse array of pathogenic fungi. Previous studies have shown that secondary metabolites ginsenosides secreted by ginseng root inhibited the growth of non-ginseng pathogenic fungi including the biocontrol fungus Trichoderma harzianum, while attracted and promoted the growth of rhizosphere pathogenic fungi of ginseng, such as Cylindrocarpon destructans. The promoting growth effect by ginsenosides may be happened by changing the physiological metabolism of ginseng pathogenic fungi. The relationship between ginsenosides and the aggressiveness of fungal pathogens has sparked interest in the role and mechanism of the ginsenosides in the interaction between ginseng and rhizosphere fungi. This project intend to study the effect of ginsenosides on the physiological metabolism and cell structure of ginseng root pathogen C. destructans and nonpathogen T. harzianum, and determine the fine genome map of C. destructans using high-throughput sequencing and bioinformatics analysis. Based on that, the effect of ginsenosides on the transcriptional group, proteome and G protein signal transduction pathway of C. destructans and T. harzianum will be analyzed. Our findings may provide more evidences for the molecular mechanisms of complex interaction between host plant and rhizosphere pathogenic microorganism and beneficial microorganism. In addition, it will provide ideas for the ecological control of ginseng diseases.

名贵药用植物人参的真菌病害十分严重。前期研究发现：人参分泌的次生代谢物人参皂苷选择性吸引并促进人参根际病原真菌生长，抑制包括生防菌哈茨木霉在内的非人参病原真菌生长，人参皂苷可能通过影响人参病原真菌的生理代谢发挥了促生长作用。人参皂苷在人参-根际真菌互作中发挥的角色及其作用机制值得深入研究。本项目拟分析人参皂苷对人参根际病原菌毁灭柱孢菌和非病原菌哈茨木霉生理代谢和细胞结构的影响，采用高通量测序技术进行毁灭柱孢菌基因组精细图解析及生物信息学分析，在此基础上分析人参皂苷对毁灭柱孢菌和哈茨木霉转录组、蛋白质组以及G蛋白信号转导途径的影响，系统解析人参皂苷促进人参根际病原菌生长、抑制非病原真菌生长的生理、生化和分子生物学机理。研究结果将为理解寄主植物与根际病原微生物、有益微生物复杂互作的分子机制提供依据，也将为人参病害生态防治奠定理论基础。

我们前期研究发现，人参皂苷Rb1选择性吸引并促进人参根际病原真菌生长、抑制非人参病原真菌生长，人参皂苷可能是通过影响人参根际真菌的新陈代谢发挥了选择性促抑作用，从而对根际微生物群落结构产生选择塑造作用。人参皂苷在人参-根际真菌互作中发挥的角色及其作用机制值得深入研究。本项目系统分析了不同栽培年限的人参根际土壤中8种人参皂苷单体（Rb1、Rb2、Rc、Rd、Rg1、Re以及G-VXII和F2）含量，调查了人参皂苷与根际土壤微生物群落之间的互作规律，明确了人参皂苷Rb1对人参根际真菌生长选择性促抑的生理生化机制，系统研究了7种人参皂苷单体影响人参根际真菌生长的构效关系。结果表明，人参根分泌到土壤中的6种主要皂苷的相对含量随着栽培年限的增加而降低，而人参皂苷Rb1的降解产物G-VXII和F2的相对含量随着栽培年限的增加而增加，人参皂苷Rd、G-VXII和F2与人参根际土壤真菌群落丰度高度正相关，人参通过人参皂苷介导的对土壤微生物的化感作用是导致人参根际土壤微生态失衡的关键因素。人参皂苷Rb1促进了人参病原菌毁灭柱孢菌对培养基中总糖和蛋白质的利用，对NADH呼吸链产生了刺激作用，对其生物膜系统具有保护作用；人参皂苷Rb1对哈茨木霉的生长、营养利用、新陈代谢和细胞膜系统的作用完全相反。哈茨木霉菌体内无丙酮酸激酶（PK）活性。7种人参皂苷单体对毁灭柱孢菌的生长、营养利用、新陈代谢以及细胞膜功能产生了不同的影响。二醇型皂苷Rb1和Rb2显著促进毁灭柱孢菌的生长和营养利用，显著促进毁灭柱孢菌体内PK酶活力以及能量代谢，对细胞膜功能无不良影响；而三醇型皂苷Re、Rg1以及Rb1的代谢产物F2则显著抑制毁灭柱孢菌的生长和营养利用，F2显著抑制PK酶活力，Rg1引起了毁灭柱孢菌的膜脂过氧化。研究结果为理解根际有益微生物、病原微生物与寄主植物复杂互作的生理生化机制以及合理有效地调控根际生态系统，破解人参连作障碍提供了理论依据。