As a stem holoparasite, Cuscuta has features that differ substantially from typical plants. Cuscuta is thus an interesting subject of research.
A heterotrophic plant. Since the parasite takes water and nutrients from its hosts, most Cuscuta species cannot photosynthesize (Thus, their color is usually yellow to red). Cuscuta has minimal leaves and no roots of its own, but rather uses host photosynthetic production and root system to provide essential nutrients and water.
Sensing its environment. Cuscuta seedlings need to locate hosts in order to attach and grow. To detect hosts they have been shown to use volatile signals (1) and are responsive to light quality and touch.
The haustorium: A parasitic plant organ. The haustorium is a structure unique to parasitic plants that forms connections to the vascular system of the host. Cuscuta haustoria form from stems and are able to make connections to stems, petioles, or leaves of the host.
Exchanging signals with hosts. Cuscuta exchanges many types of molecules with its hosts, notably including macromolecules such as RNAs (2, 3) and proteins (4), through haustoria after coil around host stems. Cuscuta may even transmit systemic herbivory signals from attacked plants to unattacked plants (5).
A different type of pathogen? By taking its nutrition from a host plant, Cuscuta acts as a biotrophic pathogen. It shows some of the same types of interactions as seen in other plant pathogens, for example triggering host receptors involved in plant pathogen immunity (6) and using microRNAs as a mechanism for depression host defenses (7).
Cuscuta is a weed. Cuscuta can severely affect yields of agricultural crops, such as legumes, tomato, and potato (8). Study of Cuscuta could lead to more effective management strategies in the field.
- Runyon JB, Mescher MC, De Moraes CM (2006) Volatile chemical cues guide host location and host selection by parasitic plants. Science 313:1964-1967.
- Kim G, LeBlanc ML, Wafula EK, dePamphilis CW, Westwood JH (2014) Genomic-scale exchange of mRNA between a parasitic plant and its hosts. Science 345:808-811.
- Alakonya A, Kumar R, Koenig D, Kimura S, Townsley B, Runo S, Garces HM, Kang J, Yanez A, David-Schwartz R, Machuka J, Sinha N (2012) Interspecific RNA interference of SHOOT MERISTEMLESS-like disrupts Cuscuta pentagona plant parasitism. Plant Cell 24:3153-3166.
- Jiang L, Qu F, Li Z, Doohan D (2013) Inter-species protein trafficking endows dodder (Cuscuta pentagona) with a host-specific herbicide-tolerant trait. New Phytologist 198:1017-1022.
- Hettenhausen C, Li J, Zhuang H, Sun H, Xu Y, Qi J, Zhang J, Lei Y, Qin Y, Sun G, Wang L, Baldwin IT, Wu J (2017) Stem parasitic plant Cuscuta australis (dodder) transfers herbivory-induced signals among plants. PNAS 114:E6703-E6709.
- Hegenauer V, Fürst U, Kaiser B, Smoker M, Zipfel C, Felix G, Stahl M, Albert M (2016) Detection of the plant parasite Cuscuta reflexa by a tomato cell surface receptor. Science 353:478-481.
- Shahid S, Kim G, Johnson NR, Wafula E, Wang F, Coruh C, Bernal-Galeano V, Phifer T, dePamphilis CW, Westwood JH, Axtell MJ (2018) MicroRNAs from the parasitic plant Cuscuta campestris target host messenger RNAs. Nature 553:82.
- Costea M, Tardif FJ (2006) The biology of Canadian weeds. 133. Cuscuta campestris Yuncker, C. gronovii Willd. ex Schult., C. umbrosa Beyr. ex Hook., C. epithymum (L.) L. and C. epilinum Weihe. Canadian Journal of Plant Science 86:293-316.
Plants of the genus Cuscuta are listed as Federal Noxious weeds by the U.S. government. The genera is also listed U.S. Regulated Plant Pest Table. As such, the import to the U.S. and the interstate movement of these plants is restricted. Nevertheless, Cuscuta can be obtained for research purposes without great difficulty.
Many species of Cuscuta, including the C. campestris that we use as our main research organism, are native to the U.S. The simplest way to obtain the parasite is to acquire it within your own state, either from the wild or from other researchers. For more information, including an world distribution map, see the CABI website on C. campestris. The most challenging aspect of this may be accurate identification of the Cuscuta species, which can be difficult due to the lack of clearly distinguishing morphological features.
To import Cuscuta from other states or outside the U.S., apply for a P526 (Permit to Move Live Plant Pests, Noxious Weeds, and Soil).