Simplifying plant gene silencing and genome editing logistics by a one-Agrobacterium system for simultaneous delivery of multipartite virus vectors

Viral vectors provide a quick and effective way to express exogenous sequences in eukaryotic cells and to engineer eukaryotic genomes through the delivery of CRISPR/Cas components. Here, we present JoinTRV, an improved vector system based on tobacco rattle virus (TRV) that simplifies gene silencing and genome editing logistics. Our system consists of two mini T-DNA vectors from which TRV RNA1 (pLX-TRV1) and an engineered version of TRV RNA2 (pLX-TRV2) are expressed. The two vectors have compatible origins that allow their cotransformation and maintenance into a single Agrobacterium cell, as well as their simultaneous delivery to plants by a one-Agrobacterium/two-vector approach. The JoinTRV vectors are substantially smaller than those of any known TRV vector system, and pLX-TRV2 can be easily customized to express desired sequences by one-step digestion-ligation and homology-based cloning. The system was successfully used in Nicotiana benthamiana for launching TRV infection, for recombinant protein production, as well as for robust virus-induced gene silencing (VIGS) of endogenous transcripts using bacterial suspensions at low optical densities. JoinTRV-mediated delivery of single-guide RNAs in a Cas9 transgenic host allowed somatic cell editing efficiencies of ≈90%; editing events were heritable and >50% of the progeny seedlings showed mutations at the targeted loci.

In search of: Suggesting a course of action for the scientific community to research potential impacts of heritable gene editing on the maternal carrier

Prospective parents with a high risk of transmission of a disease-causing mutation may want to have an unaffected genetically related child. With advances in scientific technologies, including CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats), they may be able to do so through heritable gene editing of the human germline at the pre-implantation stage. CRISPR technology in the reproduction and fertility context could potentially correct mutations in the germline, allow for the production of embryos that are free from a mutation and terminate the transmission of a disease-causing mutation from parent to child. As reproductive technologies evolve, a gap in the available literature exists that fails to address the potential impacts of edited fetal DNA on the maternal carrier. Both critical technical issues related to employing CRISPR, and germline editing based technologies in human reproduction and long-term impacts need to be studied and clarified to ensure positive application and outcomes for both offspring and mother.