Jasmonates accumulate within seconds when plants are attacked by herbivores or experience mechanical damage. As signaling molecules they link damage associated patterns to appropriate responses in the plant body, by inducing the plant defense systems and adapting growth and development in the plant. Loss of jasmonate biosynthesis leaves the plant almost helpless against a variety of herbivores and necrotrophically living pathogens.
One of the best known characteristics of jasmonates is, that they are lowly abundant under normal growth conditions but reach high levels not only at site of the stimulus but also in distal tissues. The systemic accumulation has been the focus of many studies, which proposed that jasmonate is transported over long and short distances to induce defense responses. However, our knowledge of jasmonate transporting elements is marginal.
In this thesis, two jasmonate efflux proteins (JEFFs) were identified in a functional screen. We found that the JEFF mediated efflux is conserved in homologs of different angiosperm species. To investigate if the JEFFs are involved in jasmonate mediated defense induction, their contribution to the resistance against the herbivore Spodoptera littoralis and the fungus Botrytis cinerea was tested. Wounding assays indicate that the JEFFs are involved in systemic induction of the defense compounds glucosinolates, which may be caused by a JEFF mediated shift of jasmonate precursors to the biologically active form of jasmonates. Further, jasmonate efflux may be involved in root growth responses as well as in the regulation of leaf growth. These results underline the importance of spatio-temporal jasmonate signaling and propose that jasmonate fluxes across the plasmamembrane regulate phenotypic plasticity.