Porcine reproductive and respiratory syndrome (PRRS), also known as Blue-Ear Pig Disease, is an economically important disease induced by PRRS virus (PRRSV) in swine, which causes late-term reproductive failure and severe pneumonia in neonatal pigs. Molecular farming has a great potential since the cost for production is low and plant tissue is easy for use as food additive. The gene sequences of ORF5 corresponding to the neutralizing epitopes of PRRSV were constructed in the plant expression vector and expressed as subunit vaccines in banana and tobacco. Expected sizes of fragments were detected by polymerase chain reaction (PCR) and Southern hybridization, indicating that the ORF5 gene was integrated into the chromosomal DNA of the transgenic plants. Immunoblot analysis of proteins extracted from transgenic banana and tobacco plants were detected by PRRSV GP5 specific antibody, anti-PRRSV rabbit serum, and confirmed the expression of foreign gene. Quantification by enzyme-linked immunosorbent assay (ELISA) showed that GP5 protein levels reached 0.012% of total soluble protein in tobacco leaf samples, and 285 ng/mg, about 0.03% of total soluble protein in transgenic banana plants. Pigs fed with transgenic banana and tobacco leaves had developed immunity and showed a specific anti-GP5 response, demonstrating that GP5 proteins were expressed in plants and were able to induce the production of anti-GP5 antibodies in the pigs. To enhance the expression level and immunity of oral vaccine, ORF5 was fused with L-TB gene from E. coli. and ORF6 genes from PRRSV for expression in plants. The transformation event was validated by PCR, Southern analysis and reverse transcription polymerase chain reaction (RT-PCR). Plant-derived LTB-GP5 recombinant protein showed binding affinity to GM1 ganglioside receptor. To improve the efficiency of banana transformation system, different additives were evaluated during Agrobacterium- mediated transformation. Addition of 0.02% Pluronic F-68 while co-cultivation with Agrobacterium resulted in higher amount of GFP-expressed embryos than other treatments absent of Pluronic F-68. Another approach for enrichment of the target protein expressed in transgenic plants is through plastid transformation. Plastid transformation vectors specific for banana and tobacco were constructed, and transformed into banana and tobacco via particle bombardment. The GFP fluorescence was detected in transgenic banana embryos and tobacco leaves and roots.