In vitro salicylic acid inhibition of catalase activity in maize:: differences between the isozymes and a possible role in the induction of chilling tolerance

It has been suggested that the inhibition of catalase (CAT) (EC 1.11.1.6) by salicylic acid (SA) plays a role in mediating stress responses. In this work, it is proposed that CAT-1 and CAT-2 isozymes of maize (Zea mays L.) might differ in the nature of SA inhibition, as it was shown for 0 and 9 dpi (days postimbibition) scutellum preparations, containing mainly CAT-1 and CAT-2 isozymes, respectively. In the case of 9 dpi extract, only a weak, competitive inhibition of CAT activity was observed upon treatment with SA or several other phenolic compounds. On the other hand, CAT activity of the 0 dpi extract was inhibited to a significantly greater extent and in a non-competitive manner by SA and its analogues, except for p-hydroxybenzoic acid (pHBA), which showed the same kinetics of inhibition as for 9 dpi samples. All of the phenolic compounds but pHBA, were found to significantly increase chilling tolerance when added hydroponically to young maize seedlings. According to these results, CAT-1 might be a candidate for mediating the effect of SA on the induction of chilling tolerance in maize. Maize genotypes with varying degrees of chilling tolerance were compared: chilling-tolerant maize lines showed significant inhibition by SA, while chilling-sensitive lines were not uniform in this respect, as in the case of Mo17, catalase activity was hardly inhibited by SA, while Penjalinan showed the same rate of inhibition as the chilling-tolerant genotypes. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.