Abstract
In recent years, RNA interference (RNAi) machinery has widely been explored by plant biologists for its potential applications in disease management, plant development, and germplasm improvement. RNAi-based technologies have mainly been applied in the form of transgenic plant generation and host-induced-gene-silencing (HIGS). However, the approval of RNAi-based transgenic plants has always been challenging due to the proclaimed concerns surrounding their impacts on human health and the environment. Lately, exogenous applications of double-stranded RNAs (dsRNAs), short interfering RNAs (siRNAs), and hairpin RNAs (hpRNAs) has emerged as another technology that could be regarded as more eco-friendly, sustainable, and publicly acceptable than genetic transformation. Inside the plant cell, dsRNAs can undergo several steps of processing, which not only triggers RNAi machinery but may also involve transitive and systemic silencing, as well as epigenetic modifications. Therefore, along with the considerations of proper exogenous applications of dsRNAs, defining their final destination into plant cells is highly relevant. In this review, we highlighted the significance of several factors that affect dsRNA-induced gene silencing, the fate of exogenous dsRNAs in the plant cell, and the challenges surrounding production technologies, cost-effectiveness, and dsRNAs stability under open-field conditions. This review also provided insights into the potential applications of exogenous dsRNAs in plant protection and crop improvement.
Highlights
RNA interference (RNAi) is a natural gene silencing phenomenon and recently is being extensively used in agriculture to improve traits related to disease management, plant development, and crop improvement
Several studies have reported that induction of RNAi mechanism by exogenous double-stranded RNAs (dsRNAs), short interfering RNAs, or hairpin RNAs has the potential to protect plants against plant pathogenic viruses (Tenllado and Diaz‐Ruiz, 2001; Carbonell et al, 2008; Yin et al, 2009; Gan et al, 2010; Konakalla et al, 2016; Vadlamudi et al, 2020), fungi (Koch et al, 2016; Wang et al, 2016; Wang et al, 2017), insects (Baum et al, 2007; Li et al, 2013; Ghosh et al, 2017; Luo et al, 2017), mites, and nematodes, which could eventually reduce the ecological footprints caused by chemical pesticides
The main objective of this review is to present an overview of possible factors that might affect RNAi induction by exogenously applied dsRNAs, and to discuss the role of exogenous dsRNAs in plant RNAi regulation and their potential fate into plant cells
Summary
RNA interference (RNAi) is a natural gene silencing phenomenon and recently is being extensively used in agriculture to improve traits related to disease management, plant development, and crop improvement. Several factors could affect the efficiency of exogenously applied dsRNA-induced RNAi in plants including, but are not necessarily limited to, concentration/dose and length/size of dsRNAs, application method, delivery technique, plant organspecific activities, and stability under unseemly environmental conditions. Successful cellular uptake and subsequent initiation of target gene silencing by exogenous dsRNAs are subject to the influences of length and/or concentrations, application methods, and delivery techniques, as well as the sensitivity of plant organs to dsRNA applications (Numata et al, 2014; Dalakouras et al, 2016; Mitter et al, 2017; Dubrovina and Kiselev, 2019). Some other delivery methods like high-pressure spraying (Dalakouras et al, 2016) or direct exogenous application of naked-dsRNAs may efficiently induce plant RNAi (Li et al, 2015; Lau et al, 2015; Dubrovina et al, 2019). The efficiency of Frontiers in Plant Science | www.frontiersin.org
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