Agrobacterium tumefaciens-mediated genetic transformation is a powerful tool for plant research, but it
can be labor-intensive and time-consuming.Here, we report a protoplast-based approach to study
nucleo-cytoplasmic interactions, such as cytoplasmic male sterility/fertility restoration (CMS/Rf) and
organellar RNA editing.To test the system, we transfected the fertility restorer gene Rf5, which is involved
in the rice HL-CMS/Rf system, into rice protoplasts prepared from the HL-CMS line. As the Rf5 protein
accumulated in the transformed protoplasts, the CMS-associated transcripts were endonucleolytically
cleaved. There were much lower levels of the CMS-associated protein ORFH79 in the transfected protoplasts than in the mock-transfected protoplasts. Next, we used a dsRNA-mediated gene silencing approach
to down-regulate the pentatricopeptide protein gene MPR25, which participates in RNA editing of the
organellar transcript nad5. The editing efficiency of mitochondrial transcripts of nad5 at nucleotide
1580 was much lower in the transfected protoplasts than in the mock-transfected protoplasts. Together,
these results show that protoplast is a simple and efficient system to study interactions between the
nucleus and organelles.