In vitro and in planta Interaction Evidence between Nicotiana tabacum Thaumatin-Like Protein 1 (TLP1) and Cucumber mosaic virus Proteins

Using a yeast two-hybrid system, we identified a plant cellular factor that interacts with the proteins of the Cucumber mosaic virus (CMV). Initially 14 candidate genes were isolated from Nicotiana tabacum, using a full-length CMV 1a gene as bait. Among the candidate genes, two were encoding thaumatin-like proteins (TLP), and were designated as Nicotiana tabacum thaumatin-like protein 1 (NtTLP1). Consistent with this observation, recombinant GST-NtTLP1 protein, which was expressed and purified in E. coli, bound tightly to CMV 1a in vitro. In planta interaction was also verified via co-immunoprecipitation. Additionally, NtTLP1 specifically interacted with the CMV movement-related proteins, movement protein and coat protein, in yeast. Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that the expression of NtTLP1 increased as the result of CMV inoculation.