Focus on Metabolism: Glutathionylation and Reduction of Methacrolein in Tomato Plants Account for Its Absorption from the Vapor Phase

摘要

A large portion of the volatile organic compounds emitted by plants are oxygenated to yield reactive carbonyl species, which have a big impact on atmospheric chemistry. Deposition to vegetation driven by the absorption of reactive carbonyl species into plants plays a major role in cleansing the atmosphere, but the mechanisms supporting this absorption have been little examined. Here, we performed model experiments using methacrolein (), one of the major reactive carbonyl species formed from isoprene, and tomato (Solanum lycopersicum) plants. Tomato shoots enclosed in a jar with vapor efficiently absorbed . The absorption efficiency was much higher than expected from the gas/liquid partition coefficient of , indicating that was likely metabolized in leaf tissues. Isobutyraldehyde, isobutyl alcohol, and methallyl alcohol () were detected in the headspace and inside tomato tissues treated with vapor, suggesting that was enzymatically reduced. Glutathione () conjugates of (-) and (-) were also detected. -href="#def3" rid="def3" class=" def">GSH was essentially formed through spontaneous conjugation between endogenous href="#def3" rid="def3" class=" def">GSH and exogenous href="#def2" rid="def2" class=" def">MACR, and reduction of href="#def2" rid="def2" class=" def">MACR-href="#def3" rid="def3" class=" def">GSH to href="#def8" rid="def8" class=" def">MAA-href="#def3" rid="def3" class=" def">GSH was likely catalyzed by an NADPH-dependent enzyme in tomato leaves. Glutathionylation was the metabolic pathway most responsible for the absorption of href="#def2" rid="def2" class=" def">MACR, but when the amount of href="#def2" rid="def2" class=" def">MACR exceeded the available href="#def3" rid="def3" class=" def">GSH, href="#def2" rid="def2" class=" def">MACR that accumulated reduced photosynthetic capacity. In an experiment simulating the natural environment using gas flow, href="#def2" rid="def2" class=" def">MACR-href="#def3" rid="def3" class=" def">GSH and href="#def8" rid="def8" class=" def">MAA-href="#def3" rid="def3" class=" def">GSH accumulation accounted for 30% to 40% of the href="#def2" rid="def2" class=" def">MACR supplied. These results suggest that href="#def2" rid="def2" class=" def">MACR metabolism, especially spontaneous glutathionylation, is an essential factor supporting href="#def2" rid="def2" class=" def">MACR absorption from the atmosphere by tomato plants.