Poster: Biology & Disease Mgmt: Genetics of Resistance
A novel vector system to engineer begomovirus resistance in transgenic plants by transcriptional and post-transcriptional gene-silencing mechanisms
C. TAI (1), J. Chen (2), F. Jan (1) (1) Department of Plant Pathology, National Chung Hsing University, Taiwan; (2) Department of Agronomy, National Chung Hsing University, Taiwan
To generate transgenic plants that are highly resistant to whitefly-transmitted Tomato leaf curl Taiwan virus (ToLCTWV) and Tomato yellow leaf curl Thailand virus (TYLCTHV), plasmid vectors were constructed to induce transcriptional gene silencing (TGS) and/or post-transcriptional gene silencing (PTGS) in a transgenic plant. The intergenic region (IR) of begomovirus containing inverted repeat sequences was inserted into the intron of a tomato gene encoding a RNA-directed RNA polymerase 1 (RDR1) or a proline dehydrogenase (PDH). Expression of a GFP-RDR in construct carrying a TYLCTHV IR (IRhp), tomato intron and GFP led to nuclear localization of IRhp RNAs in plant cells after intron was spliced out and induced TGS. A C1C2C3 construct carrying the 3’end of C1 ORF and the overlapping region of C2 and C3 ORFs of TYLCTHV triggered PTGS in the cytoplasm. Infection assays revealed that constructs inducing TGS or PTGS alone displayed moderate resistance to TYLCTHV. However, C-RDRin-IR constructs carrying an IRhp, intron and C1C2C3 ORFs induced both TGS and PTGS and displayed strong resistance to TYLCTHV. Constructs carrying RDR1 introns could be easily spliced out and triggered TGS after transient expression in tobacco plants. Constructs carrying PDH intron3 had lower efficiencies in splicing and in triggering TGS. Our results indicated that a combination of inducing both TGS and PTGS in a construct shows great promise in developing resistance against plant viruses.