Harnessing <i>Agrobacterium rhizogenes</i> and mobile elements for innovative transgene-free gene editing in woody plants

Woody landscape plants are an important sector of US agriculture and play critical roles in the urban landscape by adding value to residential, public, and commercial properties. Genetic improvement of woody landscape plants is slower than that of most other crops because of long juvenility periods, heterozygosity, and resources required to grow out large populations. New breeding technologies, especially gene editing, hold great promise to complement and improve traditional breeding. This is particularly true in woody ornamental crops where the creation of transgene-free gene-edited plants would accelerate the breeding process and reduce the regulatory burden inherent with transgenic crops. In this prospective review, we propose a method to harness the power of two technologies to transform the process of woody plant gene editing. <italic>Agrobacterium rhizogenes</italic> can induce transgenic hairy roots in many plant species, while TLS (tRNA-like sequence) has been shown to facilitate the long-distance movement of transcripts from the root to the grafted scion and remain functional. We propose using <italic>A. rhizogenes</italic> to transform root tissue with mobile gene-editing components. These components would then migrate from the roots into the shoots and leaves of the plant, eliminating the need for grafting. Since only RNA, and not DNA, migrates into the upper portion of the plant, the resulting gene-edited shoot will stay transgene-free and can be propagated through either sexual or asexual methods.