Location: Chemistry ResearchTitle: A 13-lipoxygenase, TomloxC, is essential for synthesis of five carbon flavor volatiles in tomato Author
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2013
Publication Date: 2/1/2014
Citation: Shen, J., Tieman, D., Jones, J.B., Taylor, M.G., Schmelz, E.A., Huffaker, A., Bies, D., Chen, K., Klee, H.J. 2014. A 13-lipoxygenase, TomloxC, is essential for synthesis of five carbon flavor volatiles in tomato. Journal of Experimental Botany. 65(2):419-428. Interpretive Summary: Plant volatiles mediate numerous ecological interactions spanning plant defense, pollinator attraction and human taste preferences. In tomato, the emission of compounds containing five carbons, known as C5 volatiles, influence preference to humans and likely interactions with pests and pathogens yet their biosynthetic origin has remained unclear. In collaboration with researchers at the University of Florida, scientists at the Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL, have discovered that the 13-lipoxygenase enzyme, termed TomloxC, controls the biosynthesis of both six-carbon and C5 volatiles. Wound-inducible C5 volatile biosynthesis was shown to be independent of the enzyme hydroperoxide lyase. Transgenic antisense expression of the gene TomloxC strongly inhibited production of both C5 and C6 volatiles but did not significantly alter disease progression of the bacterial leaf pathogen Xanthomonas campestris. This research demonstrates that a single plant lipoxygense enzyme is responsible for both even and odd carbon-chain length volatiles and establishes stable resources for the further examination of C5 volatile function following biotic and abiotic stress.
Technical Abstract: Five carbon (C5) volatile compounds, derived from fatty acids, are among the most important contributors to consumer liking of fresh tomatoes. Despite their important roles in flavor, the genes responsible for C5 volatile synthesis have yet to be identified. Here, we show that their synthesis is catalyzed in part by a 13-lipoxygenase (LOX), TomloxC, the same enzyme responsible for synthesis of six-carbon (C6) volatiles. C5 synthesis is independent of hydroperoxide lyase (HPL); moreover HPL knock-down significantly increased C5 volatile synthesis. This LOX-dependent, HPL-independent pathway functions in both fruits and leaves. Synthesis of the C5 volatiles increases in leaves following mechanical wounding but does not increase in response to infection with Xanthomonas campestris. Large reductions in C5 and C6 volatiles in antisense TomloxC knock-down plants were observed but those reductions did not alter the development of disease symptoms, indicating that these volatiles do not have an important defensive function against this bacterial pathogen.