Increase of diamine propane in maize roots segments after cutting and methyljasmonate treatment, as a marker of polyamine secretion.

Changes of the content of free polyamine (PAs) were followed in the roots of 3-day-old maize seedlings after cutting injury and treatment with methyl jasmonate (MeJA), a wound stress signal molecule that interfered with root physiology inhibiting by 66% maize root elongation. The content of diamine propane (DAP), a product of PA catabolism, increased dramatically along the experimental time-course as a consequence of both stress factors while putrescine (PUT) level enhanced after cutting but was unaffected by MeJA treatment. Spermidine (SPD) + spermine (SPM) content decreased in cut- or MeJA-treated roots concomitant with DAP content enhancement. Reduced content of SPD+SPM was not due to an enhancement of PA catabolic enzyme activity, namely polyamine oxidase (PAO), that on the contrary was lowered by cutting and remained unaffected in MeJAtreated roots. Results suggested that cutting and MeJa treatment induced in maize roots a stress condition that stimulated PA trafficking from cell compartments to the apoplast, where PAO is located and PAs were degraded with production of DAP. The involvement of PA trafficking and degradation in the complex defence system against wound stress was hypothesised.