Nuclear Import of the Tomato Yellow Curl Leaf Virus in Tomato Plants

Tomato yellow leaf curl geminivirus (TYLCV) is a major pathogen of cultivated tomato, causing up to 100% crop loss in many parts of the world. In Israel the disease is well known and has an economic significance. In recent years viral symptoms were found in countries of the "New World" and since 1997, in Florida. Surprisingly, little is known about the molecular mechanisms of TYLCV interaction with the host plant cells. This proposal was aimed at expanding our understanding of the molecular mechanisms by which TYLCV enters the host cell nucleus. The main objective was to elucidate the TYLCV protein(s) involved in transport of the viral genomic DNA into the host cell nucleus. This goal was best served by collaboration between our laboratories one of which (V.C.) was already investigating the nuclear import of the T-DNA ofAgrobacterium tumefaciens, and the other (Y.G.) was studying the effect of TYLCV capsid protein (CP) in transgenic plants, hypothesizing its involvement in the viral nuclear entry. Three years of our collaborative work have provided signifcant data that strongly support our original hypothesis of the involvement of TYLCtr CP in viral nuclear import. Furthermore, our results have laid a foundation to study fundamental, but as yet practically unresolved, questions about the role ofthe host cell factors in the nuclear import of geminiviruses within their host plant. As a result, this research may lead to development of new approaches for plant protection based on control of TYLCV import to the host plant cell nucleus.