Impacts of methyl jasmonate on Selaginella martensii: volatiles, transcriptomics, phytohormones and gas exchange.

Abstract

Methyl jasmonate (MeJA) induces various defense responses in seed plants, but for early plant lineages, information on the potential of jasmonates to elicit stress signaling and trigger physiological modifications is limited. The spikemoss Selaginella martensii was exposed to a range of MeJA concentrations (0, 10, 25, and 50mM), and biogenic volatile organic compound (BVOC) emissions, photosynthetic rate (A) and stomatal conductance (gs) were continuously measured. In addition, changes in phytohormone concentrations and gene expression were studied. Enhancement of methanol, lipoxygenase pathway volatiles and linalool emissions, and reductions in A and gs, were MeJA dose-dependent. Before MeJA treatment, the concentration of 12-oxo-phytodienoic acid (OPDA) was seven-fold higher than Jasmonic acid (JA). MeJA treatment rapidly increased (within 30 minutes) OPDA and JA concentrations, with the latter more responsive. Some genes involved in BVOC biosynthesis and OPDA-specific response were upregulated at 0.5h after MeJA spraying, while those in JA signaling pathway were not affected. Although JA was synthesized in S. martensii, OPDA was prioritized as a signaling molecule upon MeJA application. MeJA inhibited primary and enhanced secondary metabolism; we propose that the fast-emitted linalool could serve as a marker of elicitation of stress-induced metabolism in lycophytes.