化学通讯在松材线虫侵染和扩散中的作用

The role of chemical communication in the infection and spread of pine wood nematodes (Bursaphelenchus xylophilus)

松材线虫为外来入侵种 ,由其引起的松材线虫病正在我国迅速扩散蔓延 ,造成我国部分地区松林资源的毁灭性破坏。松材线虫病的发生和流行与媒介天牛、寄主植物、共生真菌和细菌密切相关 ,松材线虫 -墨天牛 -松树 -共生微生物之间存在着广泛的化学联系 ,它们通过化学互作 ,调控松材线虫的行为 。

The pine wood nematode (Bursaphelenchus xylophilus; PWN) is an exotic invasive species. It causes pine wilt disease. Since the index case in Nanking, China (1982) it has been epidemic, spreading rapidly and destroying Chinese pine forests. Pine wilt disease requires a vector (the pine sawyer beetle) and accessory microbes, both fungi and bacteria. Extensive chemical communication adjusts the behavior of the PWN and promotes transmission. These can potentially alter the course of individual cases and thus the epidemic. Here we review the known interactions, including: (1) Chemicals produced by the pine hosts and the insect vectors attract the PWN to the beetles. These chemicals (such as unsaturated fatty acid, toluene, etc, )are hypothesized to gather PWN 3^(rd) stage larva around the pupal chambers of the sawyers and adjust the timing of PWN molting and ecdysis, and thus synchronous with adult eclosion of the sawyer beetle. (2) Chemical cues, such as exhaled CO_2, guide the nematodes into the vector's trachea. A second set of cues, including a neutral storage lipid, triggers the exiting behavior. Volatile chemicals produced by the pine (such as β-myrcene and α-pinene) also affect nematode's behaviors of exiting form the vector and entering its host pine and shuttling in the host. (3) Chemicals (e.g. ethanol, hexanol, octanol, et al, ) stimulate the growth and reproduction of PWN. (4) Chemicals stimulate the feeding behavior of the pine sawyer, and in consequence , the transmitting effects of PWN. (5) Toxins production by either the PWN, or possibly its associated microbes, kill the host pine trees. (6) Host chemicals may allow resistance to PWN. Understanding of these chemical-mediated interactions is critical to management of pine wilt disease and may also enhance our understanding of other plant pathogens.