>Magister Scientiae - MSc / In recent years, nitric oxide (NO) has emerged as an important endogenous plant
signalling molecule that mediates many developmental and physiological
processes. NO regulates the activity of antioxidant enzymes in response to droughtinduced
stress by controlling the expression of the genes that encode these enzymes.
Antioxidant enzymes function in scavenging reactive oxygen species like
superoxide ion (O2
-) and hydrogen peroxide (H2O2) that are generated in response
to drought-induced stress and other abiotic stresses. Abscisic acid, a phytohormone
that acts as a stress-related hormone in plants, also stimulates production of H2O2,
thus further triggering the antioxidant enzyme activity in order to scavenge the
excess H2O2. Accumulated data indicate that NO interacts with reactive oxygen
species, notably hydrogen peroxide and superoxide. This study was aimed at
clarifying the role of NO derived from nitric oxide synthase-like (NOS-like)
enzymatic activity in scavenging of H2O2 and to establish if this is dependent or
independent of ABA signaling. This was achieved by using Nω-Nitro-L-Arginine
methyl ester (L-NAME), an inhibitor of NOS to control the amount of NO in maize
tissue. The study investigated the effect of L-NAME on the accumulation of
superoxide, which is scavenged by superoxide dismutase. Furthermore, the study
determined the role of NOS-like activity in ABA-mediated production of H2O2.
Lastly, the effect of L-NAME on H2O2 accumulation and antioxidant enzyme
activity was also investigated. Application of L-NAME altered the enzymatic
activity of superoxide dismutase, ascorbate peroxidase and catalase. These changes
in enzymatic activity were coupled with altered levels of O2
- and H2O2 in leaves
and roots. Treatments with ABA in combination with L-NAME resulted in reversal
of H2O2 content to basal levels. These results suggest that nitric oxide, produced by
nitric oxide synthase-like activity, is important in regulation of antioxidant enzyme
activity and cross-talks with ABA.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uwc/oai:etd.uwc.ac.za:11394/6758 |
| Date | January 2018 |
| Creators | Hlatshwayo, Siphiwe Gift |
| Contributors | Ludidi, Ndomelele Ndiko, Phillips, Kyle |
| Publisher | University of the Western Cape |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Rights | University of the Western Cape |
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