Salicylic acid enhances the activity of the alternative pathway of respiration in tobacco leaves and induces thermogenicity

Abstract

A rise in the level of endogenous salicylic acid (SA) during flowering of the thermogenic voodoo lily, Sauromatum guttatum, leads to a pronounced temperature elevation by stimulation of the alternative respiratory pathway. We have studied the thermal response of tobacco (Nicotiana tabacum L.) leaves, a non-thermogenic tissue, to exogenous SA, and its relation to alternative respiration. A reproducible increase in surface temperature of 0.5-1.0 degrees C was registered with high-resolution infrared cameras. The same phenomenon was observed when 2,6-dihydroxybenzoic acid, an active analogue of SA, was used. Non-active SA analogues, such as 3- and 4-hydroxybenzoic acid, did not induce thermogenicity. The thermal effect of SA was abolished with inhibitors of the alternative pathway, such as salicylhydroxamic acid and propyl gallate. Polarographic measurement of the respiratory activity, including that of the alternative pathway in SA-treated plants, showed a significant increase of both total respiration and the alternative pathway compared with non-treated controls. Therefore, we postulate that, as in thermogenic species, SA enhances the activity of total respiration and of the cyanide-resistant pathway in tobacco leaves, subsequently leading to an elevation in surface temperature

The Effects of Salicylic Acid and Tobacco Mosaic Virus Infection on the Alternative Oxidase of Tobacco

“…The results of the present study suggst that there is an apparent regulation of the alternative oxidase that compensates for the higher amount of alternative oxidase protein present to keep the partitioning of electrons to the oxidase constant at a given total respiration rate. The respiratory data from this study differ from the results obtained by Van Der Straeten et al (1995). Eight hours after SA treatment of tobacco plants, these authors observed an increase in the total respiration rate, as well as an increase in the activity of the alternative pathway measured as the difference between total respiration and the respiration after the addition of 25 mM SHAM.…”

“…The rate of O, consumption for untreated plants obtained in this study is higher than that reported by Van Der Straeten et al (1995), the difference being approximately 35 nmol O, min-' g-' fresh weight, perhaps due to varietal differences. The respiration rates reported by Van Der Straeten et al (1995) following treatment with SA (approximately 90 m o 1 O, min-' g-' fresh weight) are closer to the rates obtained in our experiments for both treated and untreated plants. It is possible that the increase in respiration rate observed by Van Der Straeten et al (1995) was due to the different method of application of SA to their plants.…”

“…This temperature increase was proposed to be derived from the observed increase in alternative pathway activity. Van der Straeten et al (1995) reported that the overall increase in respiration upon treatment with SA was 18 nmol O 2 min" 1 g" 1 fresh weight. Assuming that the entire increase in the respiration rate occurred via the alternative pathway, application of the Stefan-Boltzmann equation (Nobel, 1983) indicates that the total heat that could potentially be produced is two orders of magnitude below that required to account for the 0.5 to 1°C temperature increase observed by Van Der Straeten et al (1995).…”

“…Van der Straeten et al (1995) reported that the overall increase in respiration upon treatment with SA was 18 nmol O 2 min" 1 g" 1 fresh weight. Assuming that the entire increase in the respiration rate occurred via the alternative pathway, application of the Stefan-Boltzmann equation (Nobel, 1983) indicates that the total heat that could potentially be produced is two orders of magnitude below that required to account for the 0.5 to 1°C temperature increase observed by Van Der Straeten et al (1995). Further, the reported increase in alternative oxidase activity was demonstrated by the addition of SHAM, which may not represent a true measure of Val, in vivo in the absence of inhibitors (Day et al, 1996).…”

“…Recently, Van Der Straeten et al (1995) studied the response of tobacco leaves to exogenous application of SA. Using a high-resolution IR camera the authors recorded a 0.5 to 1.0"C rise in the surface temperature of the tobacco leaves following SA treatment.…”