Taken together, these observations demonstrated that when bound to PEI 30 -SWCNT, some or all functional units of the plasmid DNA are not accessible to the cellular machinery as a single unit for replication and expression. Similarly, the large functional unit residing on the plasmid DNA is not available for transcription to initiate the RNA-based genomic replication of TRV and PVX viruses. These results indicate that DNA condensation on PEI-SWCNT does not allow the release of DNA, and the bound DNA is not available as a single unit for replication and transcription machinery. Since these findings may imply a fundamental limitation of the PEI-SWCNT-based in planta expression of large plasmids, we decided to conduct a deep investigation of the mechanisms of binding, release, and expression of DNA. VIGS plasmids in Agrobacterium were used as a positive control, and VIGS plasmids DNA only was infiltrated directly as a negative control to deliver the same binary vector into N. benthamiana leaves. Photos of the top developing leaves were taken 14 days after infiltration. c) Systemic expression of GFP in N. benthamiana plants. The PVX-GFP clone was conjugated with the PEI 30 -SWCNT and infiltrated into leaves of 3-week-old N. benthamiana plants. The PVX-GFP binary vector in Agrobacterium was used as a positive control, and PVX-GFP plasmids DNA only was infiltrated directly as a negative control to deliver the same binary vector into N. benthamiana leaves. Photographs were taken under UV light 14 days after infiltration.