Isoprene Discovered to be an Antioxidant
A fraction of net carbon assimilation can be re-released as isoprene by many tropical plants; however, much uncertainty remains about its biological significance. A comprehensive analysis of the suite of isoprene oxidation products in plants has not been performed and production relationships with environmental stress have not been described. Traditionally, isoprene is assumed to only be oxidized in the atmosphere to methyl vinyl ketone, methacrolein, and 3-methly furan. Abiotic stress (e.g., high temperature, light, and freeze-thaw) is known to induce oxidative stress in plants. A study conducted at Lawrence Berkeley National Laboratory, in conjunction with the Department of Energy’s GOAmazon campaign in Brazil, aimed to identify and quantify emissions of potential isoprene oxidation products from mango tree leaves as a function of temperature. Isoprene oxidation products including methyl vinyl ketone, methacrolein, and 3-methyl furan were measured as direct emissions from mango trees grown in environmental chambers. Isoprene oxidation also was measured in a tropical mesocosm (Bisophere 2). These measurements were taken at the leaf, branch, mesocosm, and whole ecosystem scale using chamber and tower sampling systems. The study’s results indicate that emissions of isoprene oxidation products from plants increase with abiotic stress and may be associated with lipid peroxidation at high temperatures. The results suggest that isoprene is an important ecosystem antioxidant involved in signaling processes through the formation of reactive electrophile species. These observations highlight the need to investigate further the mechanisms of isoprene oxidation in plants under stress and its biological and atmospheric significance.
Jardine, K. J., K. Meyers, L. Abrell, E. G. Alves, A. M. Yanez Serrano, J. Kesselmeier, T. Karl, A. Guenther, J. Q. Chambers, and C. Vickers. 2013. “Emissions of Putative Isoprene Oxidation Products from Mango Branches Under Abiotic Stress,” Journal of Experimental Botany 64(12), 3669-79.