The Effect of Wounding And Methyl Jasmonate on the Expression of Lipoxygenase in Soybean Leaves

Lipoxygenase enzymes (LOXs) have been shown to catalyze the peroxidation of polyunsaturated fatty acids. Numerous LOX forms have been reported in soybeans. Several roles have been proposed for these enzymes including lipid metabolism, growth and development, senescence, defense, synthesis of regulatory molecules and nitrogen storage. Physical wounding and pathogenic infection have been reported to increase levels of some LOX forms. Previous work in this lab confirmed that physical wounding enhanced expression of LOX 5 and revealed a reduction in LOX 7 expression. In this project, we explored the time course of the effect of wounding on the expression of LOX mRNAs in wounded and systemic leaves. We also tested whether methyl jasmonate, a plant defense signal, affected the expression of LOX isoenzymes in wounded plants to understand the defense mechanism against predators. For time course studies, plants were wounded at the bifoliate stage; one leaf was wounded while the other was used as a systemic leaf. Both leaves were harvest at 3 hours or 24 hours. Leaves were also harvested from a control plant. For the effect of methyl jasmonate, plants at the trifoliate stage were wounded on both bifoliate leaves. Treated plants were exposed to methyl jasmonate in a sealed chamber. After 24 hours both sets of leaves were harvested. RNA was isolated from the tissue samples and cDNA copies were prepared by reverse transcription. Relative levels of LOX cDNAs were measured by the Quantitative Polymerase Chain Reaction using Power SYBR Green from Applied Biosystems