Cuscuta (commonly known as dodder) is a parasitic plant with an unusual growth habit. As a parasite it lives in association with at least one other plant, from which it derives all its water and nutritional needs, while providing nothing to its host in return. Cuscuta obtains its food from other plants, so it has no need for roots, leaves or photosynthesis, and appears as a network of yellow vining stems that wind around host plants. Cuscuta provides a fresh perspective for understanding plant science because its evolution to parasitism has resulted in exaggerated features that push the boundaries of plants capabilities. For example, Cuscuta seedlings can identify host locations and grow toward them, demonstrating an ability to detect and respond to other plants in their environment. Also, the ability of Cuscuta to feed off other plants creates a system in which to explore plant interactions at the cell level and to shape concepts of plant disease. Finally, the Cuscuta habit of exchanging RNA and proteins with hosts challenges our understanding of genetic regulation of individual organisms. This EDGE project aims to expand the use of Cuscuta as a research model system through development of plant transformation methods to genetically test gene function, and to provide techniques and tips on growing Cuscuta to other scientists. Growing the Cuscuta research community will promote progress in basic plant science with potential impacts in disease resistance, agricultural ecology and weed control.
The major barrier preventing the use of Cuscuta as a model plant system is the lack of a protocol for transformation and regeneration of the plant that would enable studies of gene function. The primary objective of this project is to develop transgenic Cuscuta. A few previous studies have established conditions for either Cuscuta callus transformation or regeneration from callus, but never both with the same tissue. This project focuses on systematically optimizing Cuscuta culture conditions, transformation, and regeneration to produce stably transformed parasitic plants. This will include evaluation of several Cuscuta species for amenability to transformation, along with testing Agrobacterium strains for efficiency of Cuscuta transformation. Additional approaches that aim for rapid transformation of Cuscuta without a tissue culture step (i.e., floral dip) will be tested as well. All protocols and resources will be made accessible to the broader plant community through a project website and through publications. Parties interested in obtaining germplasm used or generated in this project are encouraged to first contact USDA-APHIS regarding how to obtain permission to work with these species.
