Plant Growth Regulators, Viruses and Plant Growth

Virus infection alters plant growth and development. The role of plant growth regulators (PGRs) in control of these processes in diseased plants is reviewed, taking tobacco mosaic virus infections of tobacco and tomato as the main model systems. Growth inhibition was related primarily to severity of visible mosaic symptoms rather than to the extent of virus multiplication. In tobacco, infection increased abscisic acid and decreased active cytokinin concentration, thus inhibiting cell division activity and reducing plant growth. Changes in other growth regulators after infection are briefly reviewed. Auxin and gibberellin activity are generally decreased by infection in diverse combinations of plants and viruses, while ethylene production is stimulated in hypersensitive reactions to infection. The chloroplast may be a major site of interaction between the virus and PGR metabolism.