Identification of Plant Genes Involved in TYLCV Replication

Since there are still no chemicals that can be applied routinely to control plant virus diseases, TYLCV control strategies have been mainly focused on methods to prevent the occurrence of infection and on genetic resistance. Attempts to reduce the incidence of TYLCV by eliminating the sources of inoculum or controlling vector transmission are often ineffective (Picó et al., 1996). Attempts to derive TYLCV resistant tomato cultivars constituted the main effort of extended breeding programmes to introgress resistance from wild Lycopersicon species. Although some wild relatives of tomato are resistant, introduction of resistance traits into commercial tomatoes is however complicated by several factors. Some tolerant cultivars have been released (Lapidot et al., 1997; Friedmann et al., 1998), but no fully resistants Lycopersicon esculentum are still available.

The identification of plant genes involved in the viral life cycle may offer the opportunity to disrupt the interaction between the virus and the plant cell, thus preventing infection without introducing foreign genes in the plant. Despite differences in the properties of their genomes, all plant viruses face the same two fundamental challenges during the establishment of systemic infections in their plant hosts. The first necessity is to replicate in the infected cells. The second requirement is to move through adjacent plant cells to the vascular system, before spreading throughout the plant. Both processes depend on highly specific interactions with host proteins. Protein-protein interactions are the underpinnings of a vast number of these cellular processes. In recent years, the convergence of biochemistry, cellular and molecular biology has made available a number of powerful techniques for studying such interactions. These techniques vary in their sensitivity, efficiency and rapidity, but judicial deployment of a combination of them has proved to be effective and reliable.