Parasitic Plants

Parasitic Plants

Dodder parasitizing a host plant.

Dodder parasitizing a host plant.

Ongoing research at Virginia Technical University performed by Jim Westwood, professor of plant pathology, weed science and physiology, suggests that plants may use a sophisticated method of communication which allows them to share vast amounts of genetic information. Researching and interpreting how plants communicate at a molecular level can provide insight for combating parasitic weeds which can threaten and destroy crops. In his study published this month in the journal “Science” (http://www.sciencemag.org/content/345/6198/808.full?sid=ac6c491d-b2f1-4844-b448-7aa2551d776c), Westwood investigates the relationship between the parasitic plant, dodder (Cuscuta spp.) and two host plants, Arabidopsis and tomatoes. During dodder’s parasitic hold on its host plant it uses a “haustorium”-highly modified stem or root of a parasitic plant, to penetrate the plant sucking out moisture and nutrients, concurrently the plants are also exchanging RNA (Ribonucleic acid: used to convey genetic information from DNA to the proteins produced by the cell). RNA can be involved in coding, decoding, regulation and expression of genes, but Westwood’s work has found that messenger RNA molecules, the molecules responsible for translating information from DNA, were being exchanged by the thousands during a parasitic interaction.

Close up cross-section of dodder where penetration of host material can be seen.

Close up cross-section of dodder where penetration of host material can be seen.

Tendrils of the dodder wrapped around the stem of an Arabidopsis plant.

Tendrils of the dodder wrapped around the stem of an Arabidopsis plant.

Previous knowledge about RNA stated that these were fragile, short-lived molecules making inter-species transfer seemingly impossible. However, it seems that the parasitic connection is opening a free dialogue, where both plants are exchanging information.  It is still as of yet, unclear to Westwood exactly what the plants may be saying via these communications; perhaps the parasitic plant is telling the host plant what to do, lowering its defenses and making it easier to attack? That is the question his continued research aims to investigate, sponsored by the National Science Foundation.  This finding also begs the question, do fungi and bacteria also exchange mRNA through their interactions, although not always parasitic?

The positive ramifications of this research are very real and can be incredibly beneficial, especially in poorer regions where crops are precious and pest control not as widely available. Witchweed (Striga spp.)and broomrape (Orobanche spp.) are parasitic plants that plague agricultural efforts in some of the poorest areas of Africa and elsewhere. Westwood’s findings could help develop new, more effective control methods based on disrupting mRNA transmissions and take a step in the direction of solving food scarcity around the globe.