Host‐induced gene silencing: a tool for understanding fungal host interaction and for developing novel disease control strategies

Abstract

Recent discoveries regarding small RNAs and the mechanisms of gene silencing are providing new opportunities to explore fungal pathogen-host interactions and potential strategies for novel disease control. Plant pathogenic fungi are a constant and major threat to global food security; they represent the largest group of disease-causing agents on crop plants on the planet. An initial understanding of RNA silencing mechanisms and small RNAs was derived from model fungi. Now, new knowledge with practical implications for RNA silencing is beginning to emerge from the study of plant-fungus interactions. Recent studies have shown that the expression of silencing constructs in plants designed on fungal genes can specifically silence their targets in invading pathogenic fungi, such as Fusarium verticillioides, Blumeria graminis and Puccinia striiformis f.sp. tritici. Here, we highlight the important general aspects of RNA silencing mechanisms and emphasize recent findings from plant pathogenic fungi. Strategies to employ RNA silencing to investigate the basis of fungal pathogenesis are discussed. Finally, we address important aspects for the development of fungal-derived resistance through the expression of silencing constructs in host plants as a powerful strategy to control fungal disease.

Host-Induced Gene Silencing in Barley Powdery Mildew Reveals a Class of Ribonuclease-Like Effectors

“…The use of HIGS to identify B. graminis genes that contribute towards pathogenic development was introduced and validated by Nowara and colleagues (2010) and has also been used as a functional assay in other fungal pathosystems (Nunes and Dean 2012). We chose to measure the impact of HIGS of BEC on HI.…”

“…In the same study, silencing of two fungal β1,3-glucanosyltransferases that are coordinately upregulated during the early infection stages (Both et al 2005) similarly decreased powdery mildew development (Nowara et al 2010). Used increasingly to investigate a number of plant-pathogen interactions, it is assumed that HIGS is mediated by specific RNA interference (RNAi) driven by double-stranded RNA transferred from the host to the closely interacting pathogen, but the precise mechanism is not yet understood (Nunes and Dean 2012).…”

Gene silencing and gene expression in phytopathogenic fungi using a plant virus vector

“…These processes, commonly referred to as RNAi, play a natural role in the regulation of endogenous gene expression, development, and maintenance of genome integrity and stability in reproductive cells, and in the protection against transposable elements and viral infections. Besides its biological role, RNAi was recognized rapidly as a powerful approach for elucidating gene functions in a variety of organisms, including phytopathogenic fungi (5,6). In these organisms, RNAi has been induced mainly with siRNAs derived from constructs expressing dsRNAs or hairpin RNAs (hpRNAs) delivered through plasmids or sequences integrated in fungal or plant genomes (7).…”

“…transfection | plant pathogen adaptation | host species jump R NA interference (RNAi), RNA silencing, and gene quelling are conserved processes in animals (1), plants (2), and filamentous fungi (3), where they operate through diverse pathways based on a set of core reactions (4,5). Briefly, these include the synthesis of a double-stranded RNA (dsRNA), which is recognized and diced into 21-to 25-long dsRNA fragments by conserved ribonucleases of the Dicer-like protein family.…”

“…Briefly, these include the synthesis of a double-stranded RNA (dsRNA), which is recognized and diced into 21-to 25-long dsRNA fragments by conserved ribonucleases of the Dicer-like protein family. The small fragments denoted small interfering RNAs (siRNA) are then loaded onto members of the Argonaute protein family to form an RNA-induced silencing complex that uses one of the two strands of the siRNAs to direct RNA degradation, translational repression, or DNA methylation of homologous target genes (4,5). These processes, commonly referred to as RNAi, play a natural role in the regulation of endogenous gene expression, development, and maintenance of genome integrity and stability in reproductive cells, and in the protection against transposable elements and viral infections.…”