ABSTRACT
Pioneering work in many aspects of molecular plant pathology such as protein purification and sequencing, X-ray crystallographic determination of structures, and nucleic acid sequencing have all been developed using plant viruses such as Tobacco mosaic virus (TMV), because of the relative simplicity of these infectious agents. Their small nucleic acid genomes (normally encoding between four and ten polypeptides) combined with their simple protein capsids (coats) has resulted in a comprehensive understanding of many of their structural properties. However, this ‘simplicity’ means that they have an absolute requirement on host cell components and metabolism for their infection cycle, and understanding the nature of this intricate signalling between viruses and plants has become the major focus of modern molecular plant virology. In this chapter, we shall examine the structure and replication of plant viruses and other sub-microscopic infectious agents such as viroids, before discussing the ways in which they interact with host plants and vectors in Chapter 8.
