Ethylene Signaling Modulates Herbivore-Induced Defense Responses in the Model Legume Medicago truncatula

• DOI: 10.1094/mpmi-10-14-0348-r
• Publication Date: 2015-01-21T19:18:04Z
• Authors: Jamuna Risal Paudel; Jacqueline C. Bede
• Keywords: Medicago truncatula; Jasmonic acid; NPR1

One or more effectors in the labial saliva (LS) of generalist Noctuid caterpillars activate plant signaling pathways to modulate jasmonate (JA)-dependent defense responses; however, exact mechanisms involved have yet be elucidated. A potential candidate this phytohormone interplay is ethylene (ET) pathway. We compared biochemical and molecular responses model legume Medicago truncatula ET-insensitive skl mutant herbivory by fourth instar Spodoptera exigua (Hübner) with intact impaired LS secretions. Cellular oxidative stress increases rapidly after herbivory, as evidenced changes oxidized-to-reduced ascorbate (ASC) glutathione (GSH) ratios. The caterpillar-specific increase GSH ratios LS-specific ASC are alleviated mutant, indicating that ET required. Ten hours postherbivory, markers JA JA/ET differentially expressed; MtVSP induced MtHEL repressed a caterpillar LS- ET-independent manner. In contrast, expression classic marker systemic acquired resistance pathway, MtPR1, LS-dependent requires signaling. Caterpillar further suppresses induction JA-related trypsin inhibitor activity an ET-dependent Findings suggest LS-dependent, salicylic acid/NPR1-mediated attenuation JA-dependent responses.