Polyamines in plants: An overview

This article presents an overview of the role of polyamines (PAs) in plant growth and developmental processes. The PAs, putrescine, spermidine and spermine are low molecular weight cations present in all living organisms. PAs and their biosynthetic enzymes have been implicated in a wide range of metabolic processes in plants, ranging from cell division and organogenesis to protection against stress. Because the PA pathway has now been molecularly and biochemically elucidated, it is amenable to modulation by genetic approaches. Genes for several key biosynthetic enzymes namely, arginine decarboxylase, ornithine decarboxylase and S-adenosyl methionine decarboxylase have been cloned from different plant species, and antibodies to some genes are now available. Both over-expressed and antisense transgenic approaches to PA biosynthetic genes have provided further evidence that PAs are required for plant growth and development. However, molecular mechanisms underlying PA effects on these processes remain unclear. Analysis of gene expression by using DNA microarray genomic techniques should help determine the precise role of these compounds. The potential of proteomics to unravel the role of PAs in particular cellular processes has also been examined. The extensive use of the two-hybrid system and other proteomic approaches will provide new insights into the role of PAs in signal transduction. Furthermore, there is evidence that proteomics provides an excellent tool for determining supramolecular organizations of PA metabolic enzymes which may help in understanding homeostatic control of this metabolic pathway.