Most plants are what we call in the scientific jargon autotrophs. They make their own food. They use the light to power up chemical reactions that produce sugars. Most, but not all. Some plants have become parasites and lost the ability to perform these chemical reactions known as photosynthesis. Instead they penetrate the tissues of other plants and tap into these plants’ sugar supplies. Of course, this doesn’t do much good to the plants whose sugars are being stolen. And when it affects the growth of agricultural crops, that’s not good for us. For now there’s no strategy to control parasitic plants that works well but researchers might have found a way by silencing genes in the parasitic plants.
RNA interference is one way to silence genes. To be expressed a gene is first copied under the form of a messenger RNA and then translated into a protein. RNA interference relies on small RNA molecules that can bind the messenger RNA of specific genes with the consequence of hindering the production of their protein. Researchers frequently use RNA interference as a tool. By genetically modifying cells and organisms so that they produce small RNAs that bind their gene of interest, they can decrease its expression in order to study its function. In the case of the parasitic plants RNA interference works well because it’s not just sugars that are transported from the host plant to the parasitic plant; RNA molecules also pass from one to the other. By genetically modifying host plants so they produce small RNAs that bind essential genes of the parasitic plants, it might be possible to prevent the parasites from growing or at least seriously hinder their development.
Researchers tried this strategy with the parasite dodder (Cuscuta pentagona) and tobacco (Nicotiana tabacum) as the host. They targeted for silencing genes that are specifically expressed during the formation of the haustorium, the structure with which parasitic plants penetrate host tissues. And it worked. The parasites didn’t grow well on the modified tobacco plants, their haustoria could not properly connect with the host tissues and, although they still managed to flower, the number of seeds they produced was much lower.
Alakonya A et al. (2012). Interspecific RNA Interference of SHOOT MERISTEMLESS-Like Disrupts Cuscuta pentagona Plant Parasitism. The Plant Cell, 24 (7), 3153-3166 DOI: 10.1105/tpc.112.099994