Levels of Active Oxygen Species Are Controlled by Ascorbic Acid and Anthocyanin in Arabidopsis

Abstract

Stabilization of the levels of active oxygen species (AOS) is important to the survival of organisms. To clarify the system controlling levels of AOS in plants, this study used an electron spin resonance (ESR) method to directly measure superoxide radical (O(2)(.-)) scavenging activities in the wild-type Arabidopsis thaliana (Col and Ler ecotypes), two anthocyanin mutants (tt3 and ttg1), and an ascorbic acid mutant (vtc1). Under ordinary growth conditions, Arabidopsis contained superoxide-scavenging activity (SOSA) of approximately 300-500 SOD units/g of fresh weight. The ESR pattern indicated that most (40-50%) of this activity was due to ascorbic acid. For the analysis of SOSA under conditions of oxidative stress, synthesis of AOS was induced by gamma-irradiation. The radical scavenging activity in irradiated plants increased approximately 10-fold following an associated increase in the accumulation of ascorbic acid and anthocyanin. The accumulation of ascorbic acid and anthocyanin was suppressed by treatment with an antioxidant before irradiation and was induced by treatment with a radical-generating reagent. The contributions of ascorbic acid and anthocyanin to the total superoxide radical scavenging activity differed among ecotypes. In the Ler ecotype, ascorbic acid accumulated at twice the level of that in the Col ecotype, and induction of anthocyanin was half that in Col. To confirm the activity of ascorbic acid and anthocyanin against AOS stress, the viability of the wild type and mutants (tt2, tt3,tt5, ttg1, and vtc1) was examined after gamma-irradiation. Only the plants in which ascorbic acid and anthocyanin were induced had the ability to grow and flower.

Generation of Hydrogen Peroxide in Chloroplasts of Arabidopsis Overexpressing Glycolate Oxidase as an Inducible System to Study Oxidative Stress

“…Anthocyanins have been shown to act as a "sunscreen," protecting cells from high light damage by absorbing blue-green light, thereby protecting the tissues from photoinhibition (Steyn et al, 2002;Nagata et al, 2003). In agreement with this, the retarded accumulation of anthocyanins of the GO plants can also contribute to the almost arrested growth of these plants during the first 14 d in high light.…”

Expression of antiapoptotic genes bcl-xL and ced-9 in tomato enhances tolerance to viral-induced necrosis and abiotic stress

“…This finding may be the result of a strict temperature range that triggers anthocyanin synthesis (32). Reactive oxygen species are known to be generated by chilled plants as well as in leaf senescence (33,34). Reactive oxygen species are recognized as signaling molecules in activating PCD during normal development and during the responses to abiotic and biotic stress.…”

“…Reactive oxygen species are recognized as signaling molecules in activating PCD during normal development and during the responses to abiotic and biotic stress. Anthocyanins, as strong antioxidants, have been suggested as reactive oxygen species scavengers in plant tissues (33). Therefore, the accumulation of anthocyanins in the leaves of transgenic tomato plants at low temperature may further protect plants from reactive oxygen species damage and enhance cell survival.…”

Tissue- and isoform-specific phytochrome regulation of light-dependent anthocyanin accumulation in Arabidopsis thaliana

“…7 Additionally, anthocyanins are important antioxidant molecules and aid in protecting plants from damage by active oxygen species. 8 Among external stimuli, light is one of the most important environmental factors regulating the expression of flavonoid structural genes. 1,9 Biosynthesis and accumulation of pigments, including anthocyanins, is one of the main aspects of photomorphogenesis, i.e., light-regulated growth and development, in Arabidopsis seedlings upon emergence into the light environment.…”