Polyamines are small ubiquitous molecules that have been involved in nearly all developmental processes, including the stress response. Nevertheless, no direct evidence of a role of
polyamines in the
wound response has been described. We have studied the expression of genes involved in
polyamine biosynthesis in response to mechanical injury. An increase in the expression of the
arginine decarboxylase 2 (ADC2) gene in response to mechanical wounding and
methyl jasmonate (JA) treatment in Arabidopsis was detected by using
DNA microarray and
RNA gel-blot analysis. No induction was observed for the ADC1 gene or other genes coding for
spermidine and
spermine synthases, suggesting that ADC2 is the only gene of
polyamine biosynthesis involved in the wounding response mediated by JA. A transient increase in the level of free
putrescine followed the increase in the
mRNA level for ADC2. A decrease in the level of free
spermine, coincident with the increase in
putrescine after wounding, was also observed.
Abscisic acid effected a strong induction on ADC2 expression and had no effect on ADC1 expression.
Wound-induction of ADC2
mRNA was not prevented in the JA-insensitive coi1 mutant. The different pattern of expression of ADC2 gene in wild-type and coi1 mutant might be due to the dual regulation of ADC2 by
abscisic acid and JA signaling pathways. This is the first direct evidence of a function of
polyamines in the
wound-response, and it opens a new aspect of
polyamines in plant biology.