Abstract
Fumonisin B1 (FB1) elicits programmed cell death (PCD) in plants, probably through competitive inhibition of sphingosine-N-acyltransferase. Because this inhibition may result in the accumulation of free sphingoid bases in cells, it is important to characterize the enzymes that control the intracellular levels of sphingoid bases. To assess the functional consequence of the loss of function of an Arabidopsis gene encoding sphingosine-1-phosphate lyase, AtSPL1, we characterized two independent Arabidopsis mutants (atspl1-1 and atspl1-2) with T-DNA insertions in the AtSPL1 gene. These mutants were more sensitive to FB1 than wild-type plants, suggesting that the cell levels of sphingolipid catabolites may be affected to cell death signaling. Sphingolipid synthesis is initiated by serine palmitoyltransferase (SPT) that catalyzes the condensation of serine with palmitoyl-CoA to form 3-ketosphinganine. Here, we report the expression of the SPTLC2 genes in the protoplasts from suspension-cultured tobacco BY-2 cells suspended in the solution containing FB1.
