Abstract
Small RNAs (sRNAs), a class of regulatory non-coding RNAs around 20~30-nt long, including small interfering RNAs (siRNAs) and microRNAs (miRNAs), are critical regulators of gene expression. Recently, accumulating evidence indicates that sRNAs can be transferred not only within cells and tissues of individual organisms, but also across different eukaryotic species, serving as a bond connecting the animal, plant, and microbial worlds. In this review, we summarize the results from recent studies on cross-kingdom sRNA communication. We not only review the horizontal transfer of sRNAs among animals, plants and microbes, but also discuss the mechanism of RNA interference (RNAi) signal transmission via cross-kingdom sRNAs. We also compare the advantages of host-induced gene silencing (HIGS) and spray-induced gene silencing (SIGS) technology and look forward to their applicable prospects in controlling fungal diseases.
Highlights
RNAs and microRNAs. small interfering RNAs (siRNAs) conventionally refer to a class of 20–24-nt double-stranded molecules that are processed from longer precursors, deriving from the genome or exogenous RNA sequences such as viruses and transgene transcripts [4,5]. miRNAs are single-stranded non-coding RNAs of typically 20–22-nt in length produced from primary miRNAs containing a stem-loop structure, which is mostly transcribed from regions located between protein-coding genes [6,7]
We summarized the successful application cases of spray-induced gene silencing (SIGS)-mediated gene silencing for the control of application cases of SIGS-mediated gene silencing for the control of plant pathogens (Table 2)
While it is common for organisms in biological niches to exchange RNA-silencing signals, many mechanistic aspects of these signals need further investigation to understand better how a given biological equilibrium is obtained during the sRNA crosstalk
Summary
The sRNA-mediated RNA interference (RNAi) is a regulatory mechanism conserved in eukaryotes, where sRNAs play key roles in numerous biological processes, including RNA stability and processing, biotic and abiotic stress response and the regulation of morphological and developmental events [1,2,3]. MiRNAs are single-stranded non-coding RNAs of typically 20–22-nt in length produced from primary miRNAs (pri-miRNAs) containing a stem-loop structure, which is mostly transcribed from regions located between protein-coding genes [6,7] In eukaryotes, both siRNA and miRNA are processed inside the cell by RNase III-like endonucleases named Drosha and/or Dicer, bound by Argonaute (AGO) proteins and incorporated into RNA-induced silencing complex (RISC), which, in most cases, negatively regulates target gene expression at the post-transcriptional level [2,6,7]. Both siRNA and miRNA are processed inside the cell by RNase III-like endonucleases named Drosha and/or Dicer, bound by Argonaute (AGO) proteins and incorporated into RNA-induced silencing complex (RISC), which, in most cases, negatively regulates target gene expression at the post-transcriptional level [2,6,7] In other cases, they can trigger the biogenesis of secondary siRNAs to amplify the silencing effect [8,9]. We summarize and discuss the outlook for the application of RNAi technology for crop protection and human therapy
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