CaP Nanoparticles Improve the Effect of dsRNA on Gene Expression, Growth, and Mycotoxin Production of Toxigenic Fusarium graminearum.

Fusarium species and the mycotoxins produced by them represent a significant problem for agriculture and human health. Thus, the development of novel management strategies and tools is of high importance. Spray-induced gene silencing (SIGS), based on the natural mechanism of RNA interference (RNAi), has been considered as a highly specific and ecologically safe alternative to chemical fungicides, the use of which is restricted by the emergence of resistant strains and environmental concerns. At the same time, massive application of SIGS is challenged by the degradability of RNA molecules in the environment. Nanoparticles have been widely applied to protect RNA from degradation and improve its action. The aims of this study were to evaluate whether RNAi-mediated silencing of the regulatory FgVe1 gene leads to inhibition of growth, mycotoxin production, and pathogenicity of Fusarium graminearum and whether the use of CaP nanoparticles (CaPs) as double-stranded RNA (dsRNA) carriers enhances and prolongs the silencing effect. It was shown that dsRNA treatment of fungal liquid cultures resulted in 19.78-fold silencing of FgVe1 expression as well as inhibition of expression of genes related to secondary metabolism, including those involved in trichothecene and aurofusarin biosynthesis, thus leading to a reduction in DON accumulation and changes in culture color. The results also demonstrated that naked dsRNA and CaPs:dsRNA nanocomplexes differed in their abilities to induce a high silencing effect at different time points. Naked dsRNA proved more effective in inducing silencing in the early stages of fungal growth, whereas application of nanocomplexes provided a prolonged effect up to 10 days in liquid cultures and up to 14 days on detached leaves. The obtained data can be considered as a basis for the further development of new efficient SIGS-based plant protection strategies.