When the Unfolded Protein Response takes over plant cell fate : there’s no mercy for pathogens

International audienc

Are diacylglycerol-kinases involved in cryptogein-induced early signaling events?

National audienc

Phosphatidic acid signalling in cryptogein-elicited tobacco cells

National audiencePhosphatidic acid (PA) is a conserved phopholipid second messenger involved in stress response, metabolism and development in animals and plants. PA can be either generated by phospholipase D-mediated hydrolysis of phospholipids or produced by the sequential action of phospholipase C (PLC) and diacylglycerol kinase (DGK). Biochemical and pharmacological approaches carried in our laboratory indicate that a PLC/DGK pathway is activated in tobacco cell culture elicited with the oomycetal protein cryptogein. These early signalling events taking place within the first 30 minutes following the elicitation are likely to locate in plasma membrane rafts, i.e. membrane compartment highly enriched in sterols and sphingolipids that serves as signalling platformes. PA originating from the cryptogein-induced PLC/DGK pathway is further believed to control oxidative burst through regulation of the raft-localized NADPH oxidase

Diacylglycerol kinases activate tobacco NADPH oxidase-dependent oxidative burst in response to cryptogein

SPE IPM UB INRA SUPDATInternational audienceCryptogein is a 10 kDa-protein secreted by the oomycete Phytophthora cryptogea that activates defence mechanisms in tobacco plants. Among early signalling events triggered by this microbial-associated molecular pattern is a transient apoplastic oxidative burst which is dependent on the NADPH oxidase activity of the RESPIRATORY BURST OXIDASE HOMOLOG (RBOH) isoform D. Using radioactive [33P]-orthophosphate labelling of tobacco Bright Yellow-2 suspension cells, we here provide in vivo evidence for a rapid accumulation of phosphatidic acid (PA) in response to cryptogein due to the coordinated onset of phosphoinositide-dependent phospholipase C and diacylglycerol kinase (DGK) activities. Both enzyme specific inhibitors and silencing of the phylogenetic cluster III of the tobacco DGK family were found to reduce PA production upon elicitation and to strongly decrease the RBOHD-mediated oxidative burst. Therefore, it appears that PA originating from DGK controls NADPH-oxidase activity. Amongst cluster III DGKs, the expression of DGK5-like was up-regulated in response to cryptogein. Besides DGK5-like is likely to be the main cluster III DGK isoform silenced in one of our mutant line, making it a strong candidate for the observed response to cryptogein. The relevance of these results is discussed with regard to early signalling lipid-mediated events in plant immunity

La construcción de la Hacienda hispánica en el largo siglo XVIII: una investigación en curso

Dossier monographiqueInternational audienc