Plant defence systems induced by ozone

TLDR

Plants exposed to elevated ozone undergo biochemical changes before visible damage, yet gene‑level responses are poorly understood and appear similar to pathogen‑induced defenses. The review aims to advance understanding of the molecular basis of ozone‑induced plant responses and to apply cloned defence genes and molecular tools for developing specific biomarkers for ozone injury monitoring. The authors synthesize recent molecular studies, propose applying cloned defence genes to ozone‑exposed plants, and outline using molecular biology techniques to generate sensitive biomarkers. Ozone exposure triggers increases in enzymes linked to general defense, including ethylene synthesis, polyamine metabolism, phenylpropanoid and flavonoid pathways, and antioxidant enzymes such as superoxide dismutase and peroxidases.

Abstract

ABSTRACT Recent advances in the understanding of the molecular basis of plant response to ozone attack are reviewed. Plants grown in elevated atmospheric ozone are known to undergo several biochemical 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, H 2 O 2 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.