Nitric Oxide Is Involved ABA-Induced Antioxidant Defence Of Chloroplast And Apoplast In Leaves Of Maize (Zea Mays L.) Seedlings

Nitric oxide (NO) has been proved to be protective against damages provoked by oxidative stress conditions. Abscisic acid( ABA) not only induces the expression of antioxidant defence genes but also induces the increase in the activities of antioxidant enzymes and the contents of non-enzymatic antioxidants. In this work, the roles of NO in ABA-induced antioxidant defence were investigated in leaves of maize (Zea mays L) seedlings. Treatment with ABA or SNP (sodium nitroprusside, NO donors) enhanced the activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and ascorbate peroxidase (APX). NO generation was monitored using the NO-specific fluorescent dyes 4,5-diaminofluorescein diacetate (DAF-2DA). Increased fluorescence intensity was observed in the ABA-treated leaves. Meanwhile, the application of PTIO (2-phenyl-4,4,5,5-tetramethyl-imidazoline-l-oxyl-3-oxide, NO scavenger) or L-NAME (N~G-nitro-L-argimine, NO synthesis inhibitor) reduced the ABA-induced NO production and antioxidant defence, these results suggest that NO is required for ABA-induced antioxidant defence.At subcellular level, we investigated the effects of NO on the chloroplastic and apoplastic antioxidant enzyme systems. Experimental results showed that ABA or SNP induced the chloroplastic and apoplastic antioxidant enzymes and the induction were blocked by the pre-treatment with PTIO or L-NAME. These data suggest that NO could coordinate the activities of antioxidant enzymes in different subcellular compartments by mediating the signaling transduction of ABA.