Polyamine oxidase activity contributes to sustain maize leaf elongation

RODRIGUEZ AA ; MAIALE SJ; MENENDEZ AB AND RUIZ OA

JOURNAL OF EXPERIMENTAL BOTANY

OXFORD UNIV PRESS

Año: 2009 vol. 60 p. 4249 - 4262

0022-0957

The possible involvement of apoplastic reactive oxygen species produced by free polyamines oxidation in leaf growth of salinized maize has been studied. Salt treatment increased apoplastic spermine and spermidine, mainly in the leaf blade elongation zone. Total activity of polyamine oxidase were up to 20-fold higher than that of the copper-containing amine oxidase. Measurements of H2O2, ·O2- and HO· production in presence or absence of the polyamine oxidase inhibitors 1,19-bis-(ethylamine)-5,10,15 triazanonadecane and 1,8-diaminooctane showed that in salinized plants, free apoplastic polyamines oxidation by polyamine oxidase would be the main source of reactive oxygen species in the elongation zone of maize leaf blades. This effect is probably due to increased substrate availability. Incubation with 200 µM spermine doubled segment elongation, whereas the addition of 1,19-bis-(ethylamine)-5,10,15 triazanonadecane and 1,8-diaminooctane to 200 µM spermine attenuated and reverted the last effect, respectively. Likewise, the addition of MnCl2 (a ·O2- dismuting agent) or the HO· scavenger sodium benzoate along with spermine, annulled the elongating effect of the polyamine on salinized segments. As a whole, results here obtained demonstrated that under salinity, polyamine oxidase activity provides a significant apoplastic reactive oxygen species amount which contributes to 25-30% of maize leaf blade elongation.