丛枝菌根真菌与大豆胞囊线虫的相互作用

It is now generally accepted that the symbiosis association between arbuscular mycorrhizal (AM)fungi and plant roots results in an increase of plant resistance to soil-borne pathogens. However, little is known about the mechanisms involved in AM-bioprotection. In this project, a series of studies were conducted on seedlings of soybean cultivar which is susceptible to soybean cyst nematode (SCN, Heterodera glycines) and cuttings of grape which is able to be infected by Meloedogyne incognita in order to revealed the mechanisms of increasing plant's resistance and/or tolerance to nematodes by AM fungi. Main results were showed as below: 1. The colonization with AM fungi significantly decreased the penetration rate of nematodes, and enhanced the growth of the tested plants..2. AM fungi induced and increased the activities of POD, PAL, β-1,3-glucanase and chitinase in both grape and soybean roots. Furthermore. the peaks of the activities of POD, PAL and chitinase in roots pre-inoculated with AM fungi and then with nematodes appeared just when the colonization percentage of AM fungi increased and the penetration rate of nematodes decreased rapidly, indicating that these three enzymes play an important role in the mechanisms of disease-resistance to nematodes induced by AM fungi. 3. The defense genes, PAL5 and PR protein genes Chibl and VCH3 were regulated at transcriptional level by AM fungi and the elicitation of the pathogenesis-related (PR) protein gene was associated with the induced systemic resistance (ISR) by AM fungi. The dynamic changes in expression of PAL5 and chitinase Chib1 and VCH3 mRNA was very similar to that of the corresponding enzyme activities. Moreover, AM fungi could enhance the expression of defense genes during the resistance to nematodes by plants. 4. Inoculation with AM fungi enhanced the level of SA content in grape roots. The content of SA in roots of pre-inoculated with AM fungi and later with nematodes was greatest. The production of SA in inner and outer cortexes was triggered by AM fungi firstly, then diffused through intercellular space, and accumulated in vascular tissue. So these results also confirmed that SA mediated the ISR signal transduction induced by AM fungi. 5. The promoter sequence of V.armurensis chitinase gene VCH3 was firstly isolated using adaptor-PCR, and the transcription start site was identified by primer extension analysis. 6. The SA-responsive cis-motifs were of functional importance for the expression of GUS induced by both the AM fungi and SA.Therefore, the similar GUS activities directed by SA-responsive cis-motifs in the promoter of PR protein (chignase) gene VCH3 in transgenic tobacco roots induced by both the AM fungi and SA, suggesting that SA act as the major signal molecule in the ISR signal transduction pathway induced by AM fungi. The promoter fragments were more active in vascular and epidermal tissue than in outer and inner cortexes in both cross and longitudinal sections of transgenic tobacco roots treated by SA. But the GUS activity in inner anti outer cortexes were more active or equal to that in vascular and epidermal tissues in the cross and longitudinal sections of transgenic tobacco roots inoculated with AM fungi, which was consistent with the colonization patterns of AM fungi in roots.

本项目拟在温室盆栽条件下，采用电镀技术、酶学等方法，研究丛枝菌根（AM）真菌与大豆胞囊线虫的相互作用，以及AM真菌对此类线虫的寄生程度、效应与机制。该项目的研究对于丰富AM真菌与线虫相互作用方面的理论内容、探索新的植物病原线虫生物防治途径和技术，具有重要的理论价值和经济意义。