Plant defence systems induced by ozone

Abstract

Recent advances in the understanding of the molecular hasis of plant response to ozone attack are reviewed. Plants grown in elevated atmospheric ozone are known to undergo several hiochemical changes before any actual damage can be detected. These reactions include increases in the activities of enzymes associated with general plant defence mechanisms. Ozone exposure often causes a surge in the production of the plant hormone ethylene, as well as changes in polyamine metabolism and increases in the activities of several phenylpropanoid and flavonoid pathway enzymes. The activities of superoxide dismutase and peroxidases that protect cells from the oxidative damage caused by hydroxyl radicals, H2O2 and superoxides also increase. However, ozone-induced changes in plant cells at the gene level are almost unknown. The limited data available suggest close similarities between ozone-induced and pathogen-induced defence responses in plants. Several general defence genes that have been cloned in other studies will soon be applied to studies of gene expression in ozone-exposed plants. The use of molecular biological tools in ozone research should enable the development of highly specific and sensitive molecular markers for biomonitoring ozone-induced injuries in plants. Methionine (e) AdoMe sperm idine Spermine -^ Ethylene Figure 2. Biosynthesis of ethylene and polyamines in plants.Known inhibitory (-) interactions of the pathways are indicated by the dashed lines. Ozone is known to induce ethylene synthesis, transcription of the ACC synthase gene, changes in the polyamine concentrations and induction of ADC activity. Abbreviations used: AdoMet = S-adenosyl methionine; ACC= 1-aminocyclopropane-1-carbocylic acid. Enzymes catalysing the reactions are indicated by the following numbers: 1, ACC synthase; 2, ACC oxidase; 3, AdoMet decarboxylase; 4, ornithine decarboxylase; 5, arginine decarboxylase; 6, spermidine synthase; 7, spermine synthase; 8, AdoMet syntethase.Received 2 September 1993,

A stress‐associated citrus protein is a distinct plant phospholipid hydroperoxide glutathione peroxidase

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Accumulation of small heat shock proteins, including mitochondrial HSP22, induced by oxidative stress and adaptive response in tomato cells

“…Photo-oxidative and other environmental stresses lead to the regulation of antioxydant enzymes such as superoxide dismutases (Scandalios, 1997). Besides plant pathogen interactions, the synthesis of pathogenesis-related proteins is also enhanced by OS and ozone action (Kangasjä rvi et al, 1994), as well as UV irradiation (Green and Fluhr, 1995). Surprisingly little attention has been paid to the induction of heat shock proteins (HSP) by OS in plants.…”

Impacts of ozone on Plantago major: apoplastic and symplastic antioxidant status

“…There is evidence that various reactive oxygen species (ROS) are formed following the reaction of O $ with constituents of the apoplast implying that these ROS govern the phytotoxicity of the pollutant (Grimes et al, 1983 ;Mehlhorn et al, 1990 ;Kanofsky & Sima, 1991, 1995Runeckles & Vaartnou, 1997). Consequently, antioxidant systems that are responsible for controlling the concentrations of ROS in plant tissues are considered to play an important role in mediating O $ resistance (Kangasja$ rvi et al, 1994).…”