Development and Adoption of Genetically Engineered Plants for Virus Resistance: Advances, Opportunities and Challenges

Abstract

Plant viruses cause yield losses to crops of agronomic and economic significance and are a challenge to the achievement of global food security. Although conventional plant breeding has played an important role in managing plant viral diseases, it will unlikely meet the challenges posed by the frequent emergence of novel and more virulent viral species or viral strains. Hence there is an urgent need to seek alternative strategies of virus control that can be more readily deployed to contain viral diseases. The discovery in the late 1980s that viral genes can be introduced into plants to engineer resistance to the cognate virus provided a new avenue for virus disease control. Subsequent advances in genomics and biotechnology have led to the refinement and expansion of genetic engineering (GE) strategies in crop improvement. Importantly, many of the drawbacks of conventional breeding, such as long lead times, inability or difficulty to cross fertilize, loss of desirable plant traits, are overcome by GE. Unfortunately, public skepticism towards genetically modified (GM) crops and other factors have dampened the early promise of GE efforts. These concerns are principally about the possible negative effects of transgenes to humans and animals, as well as to the environment. However, with regards to engineering for virus resistance, these risks are overstated given that most virus resistance engineering strategies involve transfer of viral genes or genomic segments to plants. These viral genomes are found in infected plant cells and have not been associated with any adverse effects in humans or animals. Thus, integrating antiviral genes of virus origin into plant genomes is hardly unnatural as suggested by GM crop skeptics. Moreover, advances in deep sequencing have resulted in the sequencing of large numbers of plant genomes and the revelation of widespread endogenization of viral genomes into plant genomes. This has raised the possibility that viral genome endogenization is part of an antiviral defense mechanism deployed by the plant during its evolutionary past. Thus, GM crops engineered for viral resistance would likely be acceptable to the public if regulatory policies were product-based (the North America regulatory model), as opposed to process-based. This review discusses some of the benefits to be gained from adopting GE for virus resistance, as well as the challenges that must be overcome to leverage this technology. Furthermore, regulatory policies impacting virus-resistant GM crops and some success cases of virus-resistant GM crops approved so far for cultivation are discussed.

An atlas of small RNAs from potato

“…However, caulimovirus sequencies represented only 1.5% of the genome even though accounting for the second most abundant sRNAs. We note that sRNAs derived from endogenized viruses have been reported in potato (Geering et al, 2014); have been suggested to be involved in virus defense (Niraula & Fondong, 2021) and may be a source of novel genetic material.…”

When an Intruder Comes Home: GM and GE Strategies to Combat Virus Infection in Plants

“…With the help of deep sequencing, a wide range of endogenization of viral genomes was observed in plants which clearly suggests the incorporation of foreign genes is not that unnatural [272]. Also, there is still a lack of evidence in support of claims of the adverse effects of GM crops on humans and animals [273].…”

Biotechnologically Engineered Plants

“…The viral coat protein is generally the most abundant protein in small single-stranded RNA viruses. Consequently, many transgenic plants have been engineered to express a small single-stranded RNA viral coat protein gene and, as a result are often protected against the systematic spread and the subsequent deleterious effects of that virus [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. It is believed that the cloned and expressed viral coat protein gene inhibits the expression of the small single-stranded RNA virus through the mechanism of RNA interference (RNAi).…”