Indoleaceticacidisresponsibleforprotectionagainstoxidativestresscausedbydroughtinsoybeanplants:Theroleofhemeoxygenaseinduction

LÓPEZ LECUBE M; NORIEGA GO; SANTA CRUZ DM; TOMARO ML; BATLLE A; BALESTRASSE KB

REDOX REPORT

MANEY PUBLISHING

Lugar: London; Año: 2014 vol. 19 p. 243 - 250

1351-0002

Objectives: The aim of this paper is on one hand to study whether indole acetic acid (IAA) could protect soybean plants against oxidative stress caused by drought, and on the other hand to know in that case whether HO-1 and NO are involved in this mechanism. This study was focused on the role of Indole acetic acid (IAA) in the defense against oxidative stress damage caused by drought in soybean plants and to elucidate whether HO-1 and NO are involved in this mechanism. IAA is an auxin that participates in many plant processes including oxidative stress defense, but to the best of our knowledge no information is yet available about its possible action in drought stress. Methods: To this end, soybean plants were treated with 8% polyethylene glycol (PEG), 100µM IAA alone and pretreated with 100µM IAA before the addition of PEG solutions. Lipid peroxidation levels (TBARS), glutathione (GSH) and ascorbate (AS) contents, catalase (CAT), superoxide dismutase (SOD) and guaiacol peroxidase (POD) activities were determined to evaluate oxidative damage. Results: Drought treatment (8% PEG) caused a significant increase in TBARS levels as well as a marked decrease in non- enzymatic (GSH and AS) and enzymatic (CAT, SOD and POD) defense system. Pretreatment with IAA prevented the alterations of stress parameters caused by drought, while treatment with IAA alone did not produce changes in TBARS levels, and GSH and AS content. Moreover, the activities of the classical enzymes involved in the enzymatic defense system (SOD, CAT and POD) remain similar to control values. Furthermore, this hormone could enhance heme oxygenase 1 (HO-1) activity (75% over the controls), and this increase is positively correlated with protein content as well as gene expression. The direct participation of HO-1 as an antioxidant enzyme was established by performing experiments in the presence of Zn-protoporphyrin IX (ZnPPIX) a well known irreversible inhibitor of this enzyme. It was also demonstrated that HO-1 is modulated by nitric oxide (NO), as shown by experiments performed in the presence of a NO-donor (sodium nitroprusside), a NO scavenger (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), or a NO synthesis inhibitor (N-nitro-l-arginine methyl ester. NAME ). Discussion: It is concluded that IAA is responsible for the protection against oxidative stress caused by drought in soybean plants through the modulation of NO levels which, in turn, enhances HO-1 synthesis and activity.