| Arbuscular mycorrhizal (AM) fungi are the most widespread and evolutionarily ancient symbiotic endomycorrhiza microorganisms, which can form symbionts with 90% of terrestrial plants. The successful establishment of arbuscular mycorrhiza constitutes a strategy to improve the nutritional status of both partners. The fungi receive fixed carbon compounds from the host plant, while the plant benefits from the association by the increased nutrient uptake (mainly phosphorus), enhanced tolerance to abiotic stress, and resistance to pests, which play a crucial role in agriculture and natural ecosystem. However the mechanism controlling AM development is largely unknown.At the early stage of establishment of arbuscular mycorrhiza between Amorpha fruticosa L. and Glomus mosseae (GM) and Glomus intraradices (GI), defense enzymes such as L-phenylalanin ammo-nialyase (PAL),β-1,3-glucanase, polyphenol oxidase (PPO) and peroxidase (POD) increase transiently. The changes of defense enzymes activities of roots inoculated with GI show relatively larger than that with GM, which suggest plant defense response inducted by AM fungi are different, meanwhile GM have a better compatibility. The malondialdehyde (MDA) of roots colonized with GI and GM inoculation decrease by 26.6% and 25.8% respectively at 25d after germination, which suggests that the AM fungi hyphae enhance the cell membrane of the root system stability and integrality rather than impair. The GlcN (Glucosamine, degradation products of chitin elicitor) increase gradually, as the defenses enzymes inactivate, which imply that the degradation of chitin elicitor may be regulation of the host's defense mechanisms in the context of this mutualistic interaction.Flavone/isoflavones are antioxidants and signal molecules involved in the development of symbiosis between AM fungi and host plant. Herein, rutin and formononetin as Flavone/isoflavones-like substances were detected in the root system of Amorpha fruticosa L. using HPLC. At the same time, at the early stage rutin increases gradually, which may be used as carbon source in the development of symbionts. On the other hand, as a defense metabolite, formononetin increase suddenly while kept in low concentration at the late stage, which played a critical role in the formation of arbuscular mycorrhiza. Furthermore, formononetin increase at high P elements, indicating P elements affect the biosynthesis of flavone/isoflavones so as to regulate the formation of arbuscular mycorrhizal symbionts.Changes of soluble proteins in the metabolic process of plants can represent the dynamic information of intracellular proteins such as the biosynthesis, denaturation and degradation of proteins. At the early stage, soluble proteins can up-grade, as well as the number of new proteins increase and some proteins disappear, accompanying with infection ratio,which are attributed to the selective gene expression in plant tissues. Some genes such as symbiosis-associated genes, pathogenesis-related protein genes could be induced to express, while some other genes be repressed, postpone express or even be shutdown, or degraded the preexistence proteins, in order to form the arbuscular mycorrhiza. |
