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

Abstract

Meeting the increasing food and energy demands of a growing population will require the development of ground-breaking strategies that promote sustainable plant production. Host-induced gene silencing has shown great potential for controlling pest and diseases in crop plants. However, while delivery of inhibitory noncoding double-stranded (ds)RNA by transgenic expression is a promising concept, it requires the generation of transgenic crop plants which may cause substantial delay for application strategies depending on the transformability and genetic stability of the crop plant species. Using the agronomically important barley—Fusarium graminearum pathosystem, we alternatively demonstrate that a spray application of a long noncoding dsRNA (791 nt CYP3-dsRNA), which targets the three fungal cytochrome P450 lanosterol C-14α-demethylases, required for biosynthesis of fungal ergosterol, inhibits fungal growth in the directly sprayed (local) as well as the non-sprayed (distal) parts of detached leaves. Unexpectedly, efficient spray-induced control of fungal infections in the distal tissue involved passage of CYP3-dsRNA via the plant vascular system and processing into small interfering (si)RNAs by fungal DICER-LIKE 1 (FgDCL-1) after uptake by the pathogen. We discuss important consequences of this new finding on future RNA-based disease control strategies. Given the ease of design, high specificity, and applicability to diverse pathogens, the use of target-specific dsRNA as an anti-fungal agent offers unprecedented potential as a new plant protection strategy.

Pathogenic potential and virulence genotypes of intestinal and faecal isolates of porcine post-weaning enteropathogenic Escherichia coli

“…Therefore, following the gene silencing treatment, plants turned to be perfectly resistant to the fungal infection. Recently, it was also demonstrated that this gene silencing procedure can also be successful by spraying plant leaves with doublestranded RNAs against fungal (Koch et al, 2016) and viral (Mitter et al 2017) pathogens. It is important to note that application of this technique allows the modification of plant traits without altering the plant's DNA.…”

RNA-based disease control as a complementary measure to fight Fusarium fungi through silencing of the azole target Cytochrome P450 Lanosterol C-14 α-Demethylase

“…This knowledge raises the possibility that plants can be protected from pathogens/pests by exogenously supplied RNA Koch et al 2016). Possible agronomic application of environmental RNA is affirmed by the high sensitivity of Fusarium graminearum (Fg) to dsRNAs and siRNAs (Koch et al 2016).…”

“…This knowledge raises the possibility that plants can be protected from pathogens/pests by exogenously supplied RNA Koch et al 2016). Possible agronomic application of environmental RNA is affirmed by the high sensitivity of Fusarium graminearum (Fg) to dsRNAs and siRNAs (Koch et al 2016). In support of this notion, spraying a 791 nt long noncoding dsRNA (CYP3RNA), which targets the three Cytochrome P450 lanosterol C-14α-demethylase (CYP51) genes FgCYP51A, FgCYP51B and FgCYP51C of Fg strongly inhibited fungal growth on barley leaves.…”

“…uptake into the interacting fungus, and iii. processing into siRNAs by fungal FgDcl-1 (Koch et al 2016).…”

“…Importantly, application of CYP3RNA to liquid in vitro cultures of Fg inhibited mycelial growth, suggesting that in vitro screenings could be used to explore novel dsRNAs and their fungal targets (Koch et al 2013(Koch et al , 2016Koch and Kogel 2014). …”