Why Sequence Triphysaria?

Weeds are ubiquitous in agriculture, and the energy expended in their control, be it grueling human labor in developing countries or agrochemical dependence in the developed, far surpasses that of any other farming practice. This project will enhance studies of plant-plant interactions that may lead to novel approaches for weed control. It has long been known that certain plants release chemicals into the soil that affect the growth and development of nearby plants, a process generally known as allelopathy. While the agricultural potential of allelopathy has often been discussed, its study has been hampered by the complexity of rhizosphere (root-zone) interactions, the difficulty of monitoring underground associations, and the elusiveness of robust responses. The overall goal of this project is to elucidate processes mediating plant-plant interactions, with the long-range objective of thoughtfully manipulating these processes to enhance crop competitiveness.

In vitro haustorium development in Triphysaria exposed to Arabidopsis root exudates

The most obvious phenotypes associated with chemical signaling between plants are manifest by parasitic species of Orobanchaceae. These plants use small molecules released by host plant roots to initiate the development of haustoria--globular root organs that attach to and invade host roots in order to rob them of water and nutrients. Haustorium development in parasite roots exposed to host factors in vitro is rapid, highly synchronous, and readily monitored by low-power microscopy. The springtime wildflower Triphysaria is an excellent model species for these studies, because it is a facultative parasite with a broad host range that includes Arabidopsis, it is diploid and amenable to classical genetic analyses, and, unlike many of its close relatives, Triphysaria has no agricultural significance and can be studied without environmental concerns.

The effects of plant parasitism can be debilitating, and some of the world’s most destructive agricultural pests are parasitic weeds. Understanding the genetic mechanisms controlling haustorium development may lead to novel strategies for controlling these devastating pests. Furthermore, the genetic study of parasitic plants provides an unparalleled opportunity to dissect the genetic components mediating plant-plant signaling.

CSP project participants: John I. Yoder (UC Davis).