Dual action of sphinganine in the plant disease resistance to bacteria

Abstract

ABSTRACTSphingolipids are ubiquitous, highly diverse molecules constituting at least 40% of plant plasma membranes. Initially known as modulators of membrane integrity, they now emerge as important players in plant responses to (a)biotic stresses. The interaction betweenArabidopsis thalianaand the bacteriumPseudomonas syringaepv.tomatoDC3000AvrRpm1(Pst AvrRpm1) culminates in the activation of a programmed cell death known as the hypersensitive response, which is part of the plant immune response. In this study, we showed that the co-infiltration ofPst AvrRpm1and sphinganine (d18:0) inArabidopsisleaves suppress the hypersensitive response. This suppression phenotype is also observed with bacteria carrying the effectors AvrB and AvrPphB but not with the ones carrying AvrRpt2 and AvrRps4. Sphingolipid-induced hypersensitive response suppression byPst AvrRpm1is correlated with the down-regulation of the geneAtNMT1encoding aN-myristoyltransferase. d18:0 does not have a direct antibacterial effect and its co-infiltration in plants does not display typical signs of immune response such as activation of salicylic acid signaling pathway and extracellular reactive oxygen species production. Biophysical studies showed that d18:0 interacts with plant plasma membrane lipids. More specifically, d18:0 disturbs plant plasma membrane organization and mechanical properties. Our results demonstrate that sphingolipids play an important role in plant resistance, especially by interfering with the plasma membrane organization and effector localization and thus disturbing their function and subsequent immune responses.