Viral factors involved in plant pathogenesis.

Plant viruses must usurp host factors/routes for their survival. Disturbances derived from this extreme dependence for host resources, together with physiological alterations associated with defensive responses, can cause, in some virus-host combinations, acute or chronic plant diseases. As the coding capacity of these biotrophic pathogens is limited, viral-encoded proteins must essentially be multifunctional proteins involved in very different steps of their life cycle, and are usually elicitors of defensive responses. Thus, most, if not all, viral-encoded proteins can act as pathogenicity determinants. Indeed, the viral proteins involved in the essential processes of their life cycle, such as replication, movement, encapsidation and transmission can be critical players of the pathogenesis process through direct or indirect interactions. This review updates our knowledge on how viral factors affect plant physiology and contribute to the development of symptomatology.