Functional Dissection of Plant-Plant Signaling in the Rhizosphere

University Of California-Davis, Davis CA

Investigators

Abstract

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.