Functional Dissection of Plant-Plant Signaling in the Rhizosphere

虽然几个世纪以来人们已经知道，一些植物通过释放到土壤中的化学物质抑制邻近植物的生长，但实际上对与植物之间地下相互作用相关的遗传或分子机制一无所知。这在很大程度上是由于难以测定不同植物之间传递的地下化学信号的影响。一种植物如何改变另一种植物的生长和发育，最明显的表现是寄生植物。 列当科的寄生植物直接侵入邻近寄主植物的根部，以掠夺它们的水分和养分。这些寄生虫利用宿主根释放的某些分子作为识别信号来识别潜在的宿主植物。寄生植物根暴露于宿主根信号的形态学上明显的变化之一是吸器的发育，吸器是寄生物特异性根器官，其功能是宿主附着、渗透和营养从宿主转移到寄生物。吸器的发育是快速的，高度同步的，完全依赖于外部宿主因素，并且可以容易地在体外监测。正在采取分子遗传学方法来确定来自宿主植物的根因子如何触发寄生虫Triphysaria中吸器的发育，Triphysaria是太平洋沿岸常见的春季一年生野花，与毁灭性的寄生杂草Striga和列当密切相关。自然种群的调查和随后的遗传分析表明，存在着可遗传的变异，在宿主因素识别内杂交种群。一组候选宿主识别基因的表达正在寄生和密切相关的非寄生植物中进行比较，以确定吸器发育的特异性遗传途径。暴露Triphysaria根纯化吸器诱导因子或结构相关的，非活性分子将进一步定义这些过程。除了确定新植物器官如何产生的进化起源外，这项工作还将导致控制有害杂草的生物学策略的发展。

While it has been known for centuries that some plants inhibit the growth of neighboring plants through chemicals released into the soil, virtually nothing is known about the genetic or molecular mechanisms associated with subterranean interactions between plants. This is due in large part to the difficulty of assaying the effects of underground chemical signal transferred between different plants. The clearest manifestations of how one plant can alter the growth and development of a second are displayed by parasitic plants. Parasitic plants in the Orobanchaceae directly invade the roots of nearby host plants in order to rob them of water and nutrients. These parasites recognize potential host plants using certain molecules released by host roots as identification signals. One of the morphologically obvious changes to parasitic plant roots exposed to host root signals is the development of haustoria, parasite specific root organs that function in host attachment, penetration, and nutrient transfer from host to parasite. Haustorium development is rapid, highly synchronous, completely dependent on external host factors, and can be readily monitored in vitro. Molecular genetic approaches are being taken to determine how root factors from host plants triggers the development of haustoria in the parasite Triphysaria, a spring time annual wildflower common throughout the Pacific Coast and closely related to the devastating parasitic weeds Striga and Orobanche. Surveys of natural populations and subsequent genetic analyses demonstrated the existence of heritable variation in host factor recognition within interbreeding populations. The expression of a candidate set of host recognition genes is being compared in parasitic and closely related non-parasitic plants to identify genetic pathways specific for haustorium development. Exposing Triphysaria roots to either purified haustorium-inducing factors or structurally related, non-active molecules will further define these processes. In addition to determining the evolutionary origins of how novel plant organs arise, this work should lead to the development of biologically based strategies for controlling unwanted weeds.