Polyamines in plant-microbe interactions

The diamine putrescine, the triamine spermidine and the tetraamine spermine are ubiquitous in plant cells. They occur in free form as cations and are often conjugated to small molecules like phenolic acids and also to various macromolecules, such as DNA and RNA. They are necessary for the successful replication of most cells and have been implicated in the regulation of senescence and morphogenesis in plants, as well as in plant responses to environmental stress. Polyamine metabolism undergoes profound changes in response to infection by fungi and viruses. In fungal infection, the pattern of changes in polyamine levels depends, in part, upon whether the fungus is a biotroph or a necrotroph. Alterations in polyamine levels in plant-virus interactions depends upon the nature of the interaction i.e. whether it is compatible or incompatible. Most of the data relates to changes in free polyamines and it is suggested that future research on polyamines in host-pathogen interactions should include careful examination of polyamine conjugates. (C) 2000 Academic Press.