The LCB2 subunit of the sphingolip biosynthesis enzyme serine palmitoyltransferase can function as an attenuator of the hypersensitive response and Bax‐induced cell death

Summary • Previous results showed that expression of the gene encoding the LONG-CHAIN BASE2 (LCB2) subunit of serine palmitoyltransferase (SPT), designated BcLCB2, from nonheading Chinese cabbage (Brassica campestris ssp. chinensis) was up-regulated during hypersensitive cell death (HCD) induced by the Phytophthora boehmeriae elicitor PB90. • Overexpression of BcLCB2 in Nicotiana tabacum leaves suppressed the HCD normally initiated by elicitors and PB90-triggered H2O2 accumulation. BcLCB2 also functioned as a suppressor of mouse Bcl-2 associated X (Bax) protein-mediated HCD and cell death caused by Ralstonia solanacearum. BcLCB2 overexpression suppressed Bax- and oxidant stress-triggered yeast cell death. Reactive oxygen species (ROS) accumulation induced by Bax was compromised in BcLCB2-overexpressing yeast cells. • The findings that NbLCB2 silencing in Nicotiana benthamiana enhanced elicitor-triggered HCD, combined with the fact that myriocin, a potent inhibitor of SPT, had no effect on Bax-induced programmed cell death, suggested that suppression of cell death was not involved in the dominant-negative effect that resulted from BcLCB2 overexpression. A BcLCB2 mutant assay showed that the suppression was not involved in SPT activity. • The results suggest that plant HCD and stress-induced yeast cell death might share a common signal transduction pathway involving LCB2, and that LCB2 protects against cell death by inhibiting ROS accumulation, this inhibition being independent of SPT activity.