Serine Palmitoyltransferase, the First Step Enzyme in Sphingolipid Biosynthesis, Is Involved in Nonhost Resistance

An overexpression screen of Nicotiana benthamiana cDNAs identified a gene for the LCB2 subunit of serine palmitoyltransferase (SPT) as a potent inducer of hypersensitive response-like cell death. The pyridoxal 5'-phosphate binding site of NbLCB2 is required for its function as a cell death inducer. NbLCB2 mRNA is accumulated after infection by nonhost pathogen Pseudomonas cichorii. Resistance of N. benthamiana against P. cichorii was compromised by treatment with an SPT inhibitor and in NbLCB2- and NbLCB1-silenced plants. These results suggest that biosynthesis of sphingolipids is necessary for the nonhost resistance of N. benthamiana against P. cichorii.