Abstract
Wounding, one of the most intensive stresses influencing plants ontogeny and lifespan, can be induced by herbivory as well as by physical factors. Reactive oxygen species play indispensable role both in the local and systemic defense reactions which enable “reprogramming” of metabolic pathways to set new boundaries and physiological equilibrium suitable for survival. In our current study, we provide experimental evidence on the formation of singlet oxygen (1O2) after wounding of Arabidopsis leaves. It is shown that 1O2 is formed by triplet-triplet energy transfer from triplet carbonyls to molecular oxygen. Using lipoxygenase inhibitor catechol, it is demonstrated that lipid peroxidation is initiated by lipoxygenase. Suppression of 1O2 formation in lox2 mutant which lacks chloroplast lipoxygenase indicates that lipoxygenase localized in chloroplast is predominantly responsible for 1O2 formation. Interestingly, 1O2 formation is solely restricted to chloroplasts localized at the wounding site. Data presented in this study might provide novel insight into wound-induced signaling in the local defense reaction.
Highlights
Various factors are known to affect deleteriously the growth and development in plants[1,2,3]
Local response to wounding comprises of oxidative damage of lipids and proteins at the wounding site, whereas systemic response mediated by hormones such as jasmonic acid, ethylene, salicylic acid, and abscisic acid is widespread over the plant tissue and organs[35]
In agreement with our data, Flor-Henry et al.[37] proposed that lipid peroxidation occurs under wounding in detached Arabidopsis leaves using ultra-weak photon emission
Summary
Various factors are known to affect deleteriously the growth and development in plants[1,2,3]. Local responses includes oxidative burst linked with cell wall reorganization or cell death[7, 8] while systemic response, imply activation of defense related genes[9], deposition of callose, accumulation of defensive proteins (mostly with enzymatic activity) and lectins[10, 11]. The released polyunsaturated fatty acid has been known to act as a substrate for lipoxygenase leading to the production of hydroperoxy polyunsaturated fatty acids (lipid hydroperoxide, LOOH)[19]. This enzyme produces precursors for several compounds important for defense reactions, including the plant hormone jasmonic acid[20, 21]. Our data revealed that in wounded Arabidopsis plants, the lipoxygenase plays a key role in the formation of 3L=O* and 1O2
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