Effects of Double-Stranded RNAs Targeting Fusarium graminearum TRI6 on Fusarium Head Blight and Mycotoxins

Abstract

Fusarium graminearum is the causal agent of Fusarium head blight (FHB), which reduces crop yield and contaminates grains with poisonous trichothecene mycotoxins, including deoxynivalenol (DON). DON functions as an important virulence factor that promotes FHB spread in wheat; therefore, reducing DON production will decrease yield losses to FHB and enhance food safety. Recent progress using topical application of double-stranded (dsRNA) to reduce F. graminearum infection has provided encouraging results. In this study, we designed and synthesized dsRNA targeting the transcription factor TRI6 (TRI6-dsRNA), which is a key regulator of DON biosynthesis. The expression of F. graminearum TRI6 was significantly reduced in detached wheat heads treated with TRI6-dsRNA solution compared to water-treated controls. Furthermore, TRI6-dsRNA treatments reduced disease and DON accumulation in inoculated detached wheat heads. Therefore, topical applications of TRI6-dsRNA on wheat heads of intact plants were assessed for their ability to reduce FHB and DON under growth chamber and greenhouse conditions. When wheat heads were treated with TRI6-dsRNA solution in growth chamber condition, TRI6-dsRNA treatments failed to prevent FHB spread. However, when wheat heads were treated with TRI6-dsRNA solution under the greenhouse condition, FHB and DON were significantly reduced, and infection was restricted to the inoculated floret. In addition, addition of TRI6-dsRNA to toxin-induction liquid media had no effect on F. graminearum DON production. Our study demonstrates that the efficacy of dsRNA applications is strongly dependent on application methods and environmental conditions.

Agrobacterium-mediated transfer of the Fusarium graminearum Tri6 gene into barley using mature seed-derived shoot tips as explants

“…The applications of the synthetic dsRNA targeting some important genes in the fungus, including cytochrome P450 lanosterol C-14α-demethylases ( CYP ) (Koch et al 2016 ), Argonaute ( AGO ) RNase protein and DICER (Werner et al 2020 ) and Tri6 (Hao et al 2021 ), may reduce the fungal infection and improve the FHB resistance in wheat and barley. However, direct spraying of dsRNA on plant surfaces can only provide a short protection window (5–20 days) against the pathogens (Mitter et al 2017 ; Worrall et al 2019 ), and the protection cannot be transmitted to the next generation.…”

“…The expression of FHB resistance is highly influenced by many environmental factors and plant morphological traits that make it extremely difficult to reproduce phenotypic results (Cuthbert et al 2006 ; Graham and Browne 2009 ; Srinivasachary et al 2009 ; He et al 2016 ). Hao et al ( 2021 ) sprayed Tri6 -dsRNA on wheat and found that the treated plants did not reduce FHB spread under controlled growth chamber conditions, but reduced FHB spread and DON production under greenhouse conditions. Wheat and barley exhibit different FHB resistance mechanisms, barley has natural resistance to reduce the spread of the fungus (type II resistance) whereas wheat combines two primary types of partial FHB resistance including type I (resistance to initial infection) and type II (Mesterházy 1995 ).…”

RNAi as a Foliar Spray: Efficiency and Challenges to Field Applications

“…Physical and biochemical barriers notably limit the entry of topically applied exogenous dsRNA into the plant leaf tissues. These barriers provide possible explanations for the inconsistency of the topical RNAi effect among different plant species, targets, and the environmental settings [ 128 , 143 ]. The interspecific variation in leaf morphologies also indicates the need for host-dependent dsRNA delivery methods, requiring case-by-case evaluation of uptake efficiency upon selection of plant host and pathogen targets for topical RNAi.…”