Ozone‐response mechanisms in tobacco: implications of polyamine metabolism
2002
Van Buuren, Marianne Louise | Guidi, Lucia | Fornalè, Silvia | Ghetti, Francesca | Franceschetti, Marina | Soldatini, Gian Franco | Bagni, N. (Nello)
• Polyamines have been suggested to counteract oxidative damage in plants. Here, we present a detailed analysis of polyamine accumulation and its relationship to photosynthetic parameters in two tobacco (Nicotiana tabacum) cultivars (ozone‐sensitive Bel W3 and ozone‐tolerant Bel B) after a single ozone pulse and after a 1‐month exposure in the open air. • Free putrescine accumulated in undamaged tissue of both cultivars, whereas putrescine conjugated to soluble and cell‐wall bound components accumulated predominantly in tissue undergoing cell death in Bel W3 plants. Accumulation was caused by a redirection of the conjugation pathway, as well as by a transient increase in arginine decarboxylase and ornithine decarboxylase specific activity. This increase seemed to be regulated at post‐transcriptional level. • Measurements of chlorophyll content and fluorescence showed that, in addition to visible necrotic lesions, Bel W3 plants suffered considerable photosynthetic damage in other parts of the leaf. • Accumulation of conjugated putrescine is part of the ozone‐induced programmed cell death response in Bel W3 plants. Ozone‐induced synthesis of free putrescine is not correlated with ozone‐resistance in Bel B plants, which are apparently impaired in signal transduction pathways that are necessary to control the cellular redox state. However, Bel B plants are able to perceive ozone stress and to induce a series of defense mechanisms without activating hypersensitive cell death.
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