Current Fungal Biology – dsRNA as a new class of fungicide?

October 19, 2016

In order to feed the growing population in the years to come, a number of challenges for plant production will have to be overcome.

Figure 1. (A) The dsRNA (CYP-dsRNA) increases resistance of detached Barley leaves over the controls (TE, GFP-dsRNA) and (B) reduces fungal growth, measured by the level of fungal DNA, as well as (C) the activity of three ergosterol producing genes (from Koch et al. 2016).

In order to feed the growing population in the years to come, a number of challenges for plant production will have to be overcome. One persistent challenge that has been approached from a number of avenues over the last 100 or so years may have just found new life: protection of plants from fungal diseases. Currently, the most popular strategies for protecting plants from fungal disease is the use of sometimes intense fungicide spray regimes where plants may be sprayed upwards of once or twice per week throughout the growing season. The use of fungicides on food products goes back to at least the mid 18th-century when Mathieu Tillet discovered that bunt of wheat could be controlled with application of lime and salt (Tillet, 1755) and today the world fungicide market tops $7.5 billion (Morton and Staub 2005). However, there is a push in the collective consciousness for more safe and sustainable methods of plant protection; considering the growth of the organic movement.

In a recent publication in the journal Molecular Plant Pathology, Dean et al. (2012) surveyed the contributors to MPP on the top ten plant fungal pathogens based on scientific and economic importance. Two of the top results were species of Fusarium which are known to contaminate grains and to produce deadly mycotoxins. Commonly controlled with azole fungicides, a new study by Koch et al. (2016) shows that the application of specially designed double-stranded RNAs (dsRNAs) that target some of the same genes as the azole fungicides are an effective method of systemic pathogen control in barley. These dsRNAs utilize aspects of both the plant vascular system and the fungal protein machinery to inactivate genes necessary for the production of ergosterols, which are necessary for growth in Fusarium graminearum. These findings add an exciting new tool to the toolbelt of both growers and plant pathologists for the continued protection of plants and sustainable growth of food across the globe.

Literature Cited:

Koch A, Biedenkopf D, Furch A, Weber L, Rossbach O, Abdellatef E, et al. (2016) An RNAi- Based Control of Fusarium graminearum Infections Through Spraying of Long dsRNAs Involves a Plant Passage and Is Controlled by the Fungal Silencing Machinery. PLoS Pathog 12(10): e1005901. doi:10.1371/journal.ppat.1005901
Morton, V. and Staub, T. (2008) A Short History of Fungicides. Online, APSnet Features. doi: 10.1094/APSnetFeature-2008-0308.
Tillet, M. (1755) Dissertation on the cause of the corruption and smutting of the kernels of wheat in the head, and on the means of preventing these untoward circumstances. Bordeaux. 150 pp. English translation by H.B. Humphrey. 1937. Phytopath. Classics 5:1-191.