[Novel concepts emerged in the development of plant virus vectors]

There are diverse plant viruses, which cause harm to the growth of almost all crops. With the in-depth research on the mechanisms of virus infection and transmission in host plants and the development of biosynthesis technology, more and more genomes of viruses have been unveiled. These research achievements not only serve as a pillar for the establishment and optimization of plant virus expression vectors but also provide a new opportunity for the research and development of unknown functional genes in host plants. In the last decade, rapid development occurred in the construction, optimization, and application of plant virus vectors. The notable progress ranges from the breakthrough research on a well-known ancient tobacco mosaic virus (TMV) vector to exploring the use of complicated negative-sense RNA virus vectors. Particularly, the application of these virus vectors in the production of plant-derived pharmaceutical proteins and the molecular breeding has garnered increasing attention. The establishment and optimization of each virus vector rely on the solid theoretical knowledge about the replication and transcription mechanisms of the viral genome, as well as the molecular interaction mechanisms between viruses and their hosts. In return, the development of plant virus vectors is conducive to revealing the interactions between viruses and their hosts in new aspects. To facilitate the understanding of the research and application of plant virus vectors, this review expounds on the design and engineering strategies of plant virus vectors, the novel functions of viral movement proteins, host immune responses to virus infections, virus-induced gene editing (VIGE), and application of virus vectors in molecular breeding. Finally, the challenges faced by the development and application of virus vectors are discussed. As the understanding of viral gene regulation and the virus-host interaction mechanisms deepens, more plant viruses with small genomes will serve to improve the grain yield and quality and the human health. The development of plant virus vector has facilitated the evolution of 'a pathogen' into 'a practical tool' that promoted innovation in plant biotechnology research.