Increased 1-Aminocyclopropane-1-Carboxylic Acid Oxidase Activity in Shoots of Flooded Tomato Plants Raises Ethylene Production to Physiologically Active Levels

Abstract

Soil flooding increased 1 -aminocyclopropane-1 -carboxylic (ACC) acid oxidase activity in petioles of wild-type tomato (Lycopersicon esculentum 1.) plants within 6 to 12 h in association with faster rates of ethylene production. Petioles of flooded plants transformed with an antisense construct to one isoform of an ACC oxidase gene (ACO1) produced less ethylene and had lower ACC oxidase activity than those of the wild type. Flooding promoted epinastic curvature but did so less strongly in plants transformed with the antisense construct than in the wild type. Exogenous ethylene, supplied to well-drained plants, also promoted epinastic curvature, but transformed and wild-type plants responded similarly. Flooding increased the specific delivery (flux) of ACC to the shoots (picomoles per second per square meter of leaf) in xylem sap flowing from the roots. The amounts were similar in both transformed and wild-type plants. These observations demonstrate that changes in ACC oxidase activity in shoot tissue resulting from either soil flooding or introducing ACC oxidase antisense constructs can influence rates of ethylene production to a physiologically significant extent. They also implicate systemic root to shoot signals in regulating the activity of ACC oxidase in the shoot.In this paper we examine the possible role of ACC oxidation in regulating ethylene biosynthesis in vegetative shoots of flooded tomato (Lycopersicon esculentum) plants.We also assess whether changes in ethylene production attributable to different levels of ACC oxidase activity are of physiological significance for the shoots of flooded plants. During soil flooding, the root environment becomes depleted of oxygen (Grable, 1966). In response, shoot systems show a wide range of physiological and biochemical changes. Some of these changes, such as petiole epinasty in tomato, may be adaptive (Armstrong et al., 1994). Epinasty can be observed within 6 to 12 h of flooding (Jackson and Campbell, 1975) and is brought about by the action of ethylene, following enhanced accumulation (Kawase, 1972) and production (Bradford and Dilley, 1978;

Ethylene Biosynthesis during Aerenchyma Formation in Roots of Maize Subjected to Mechanical Impedance and Hypoxia

“…1). English et al (1995) recently showed that ACC oxidase activity regulates ethylene production in response to flooding in tomatoes.…”

The Haemoglobin/Nitric Oxide Cycle: Involvement in Flooding Stress and Effects on Hormone Signalling

“…The diffusion of gas in water is 10 000 times slower than in air; therefore, the ethylene formed shortly after the onset of hypoxia is trapped and accumulates, reaching levels that are sufficient to promote apoptotic aerenchyma formation (Evans, 2003). Even though the positive effect of hypoxia on the activation of ACC synthase and ACC oxidase enzymes has been well documented (English et al, 1995;Banga et al, 1996), it is still not known how low oxygen stress is sensed and leads to activation of ethylene biosynthesis (Drew, 1997;Drew et al, 2000;Evans, 2003). The action of ethylene is mediated by a signalling pathway involving a unique MAP kinase cascade (Guo and Ecker, 2004).…”

1-Aminocyclopropane-1-Carboxylate Oxidase Activity Limits Ethylene Biosynthesis in Rumex palustrisduring Submergence

“…However, more recent studies have shown that in some cases ACC oxidase also plays an important role in the regulation of ethylene production, e.g. in melon (Yamamoto et al, 1995;Lasserre et al, 1996) and tomato (English et al, 1995;Barry et al, 1996). Ethylene synthesis has been shown to be influenced by feedback regulation (Yang and Hoffman, 1984).…”