Morphology effect of a novel biocompatible nucleic acid delivery nanosystem of g-CN@dsRNA for application in plant gene expression and plant virus disease protection.

Delivery of exogenous nucleic acid to intact plants is a desirable but challenging technology due to the dominant transport barrier posed by the plant cell wall. Here, we found that three different morphologies of g-CN nanomaterials synthesized from urea can assist in the delivery of exogenous nucleic acids into mature leaf cells of Nicotiana benthamiana. Among these, g-CN carbon dots (CDs) showed a higher ability to deliver exogenous nucleic acid compared to nanoporous and g-CN nanosheets. The delivery ability of exogenous dsRNA and plasmid DNA by g-CN could also be restrained by stomatal closure and the endocytosis pathways in plant cells. Furthermore, the coupling of g-CN CDs with dsCP (CDs@dsCP), which is the dsRNA matching a specific fragment of the Coat protein-encoding gene of TMV, resulted in a superior antiviral effect compared with other morphologies of g-CN@dsRNAs and other loaded dsRNAs, which match Replicase, RNA-dependent Replicase or Movement protein of TMV. Significantly, a single spray of CDs@dsCP provided virus protection for at least 5 days. In addition, the g-CN CDs and g-CN CDs@dsRNA had no adverse effects on plant growth and development. Overall, our study presents a novel biocompatible and convenient tool for gene expression or gene silencing in intact plant leaves by spraying g-CN nanomaterials encapsulated with DNA or dsRNA, the efficiency of which is affected by the morphology of the g-CN nanomaterial, stomatal state and plant endocytosis pathway, and a highly promising solution for plant virus disease, which is an unsolved problem in plant disease control.