N Protein of Tomato Spotted Wilt Virus Proven to Be Antagonistic Against Tomato Yellow Leaf Curl Virus in <i>Nicotiana benthamiana</i>

Two phylogenetically unrelated viruses transmitted by different insect vectors, tomato spotted wilt virus (TSWV) and tomato yellow leaf curl virus (TYLCV), are major threats to tomato and other vegetable production. Although co-infections of TSWV and TYLCV on the same host plant have been reported on numerous occasions, there is still lack of research attempting to elucidate the mechanisms underlying the relationship between two viruses when they coexist in the same tomato or other plants. After assessing the effect of four TSWV-coded proteins on suppressing TYLCV in TSWV N transgenic Nicotiana benthamiana seedlings, the TSWV N protein proved to be effective in reducing TYLCV quantity and viral symptoms. Western blot analysis indicated that TSWV N was involved in down-regulating the expression level of the V1, C3, and C4 proteins of TYLCV, among which V1 was the most significantly suppressed one. Moreover, TSWV N was confirmed to reduce TYLCV V1 within both nucleus and cytoplasm, but a greater suppression was observed in cytoplasm. The co-immunoprecipitation and mass spectrometry identified 244 differential proteins from the TYLCV-infected TSWV N transgenic N. benthamiana seedling. These proteins pertaining to energy metabolism pathways were enriched, suggesting that TSWV N could inhibit TYLCV through competing for energy or regulating energy-related metabolism. The evidence presented here offers a novel perspective that will facilitate a comprehensive understanding of virus-virus and virus-host interactions, as well as a potential strategy for plant virus control through using TSWV N in the near future.