Virus-Induced Genome Editing (VIGE): One Step Away from an Agricultural Revolution

Abstract

There is currently a worldwide trend towards deregulating the use of genome-edited plants. Virus-induced genome editing (VIGE) is a novel technique that utilizes viral vectors to transiently deliver clustered regularly interspaced short palindromic repeat (CRISPR) components into plant cells. It potentially allows us to obtain transgene-free events in any plant species in a single generation without in vitro tissue culture. This technology has great potential for agriculture and is already being applied to more than 14 plant species using more than 20 viruses. The main limitations of VIGE include insufficient vector capacity, unstable expression of CRISPR-associated (Cas) protein, plant immune reaction, host specificity, and reduced viral activity in meristem. Various solutions to these problems have been proposed, such as fusion of mobile elements, RNAi suppressors, novel miniature Cas proteins, and seed-borne viruses, but the final goal has not yet been achieved. In this review, the mechanism underlying the ability of different classes of plant viruses to transiently edit genomes is explained. It not only focuses on the latest achievements in virus-induced editing of crops but also provides suggestions for improving the technology. This review may serve as a source of new ideas for those planning to develop new approaches in VIGE.

Keywords: CRISPR/Cas; RNA-dependent RNA polymerase; genome editing; transgene-free technologies; viral vector; virus-induced genome editing.

Figure 1

A scheme of agroinfiltration with (A) tripartite and (B) monopartite viral vectors. In brief, parts of the viral genome are introduced inside the T-DNA borders of one or several plasmids along with the Cas gene and gRNA cassette. The resulting vectors are cloned into A. tumefaciens via electroporation. One or several agrobacterium clones are used for agroinfiltration of plant leaves.

Figure 2

Decision tree algorithm illustrating the possibilities of improving VIGE. Depending on the characteristics of the virus, several approaches (application of small Cas protein, mobile elements, immunity suppressors, multivirus system, removal of movement protein, and improvement of RdRp) can be used for transgene-free, tissue-culture-free genome editing. The red arrows represent negative answers, and the green arrows represent positive answers.