Knockout of Arabidopsis ACCELERATED-CELL-DEATH11 encoding a sphingosine transfer protein causes activation of programmed cell death and defense

Abstract

We describe the lethal, recessive accelerated-cell-death11 Arabidopsis mutant (acd11). Cell death in acd11 exhibits characteristics of animal apoptosis monitored by flow cytometry, and acd11 constitutively expresses defense-related genes that accompany the hypersensitive response normally triggered by avirulent pathogens. Global transcriptional changes during programmed cell death (PCD) and defense activation in acd11 were monitored by cDNA microarray hybridization. The PCD and defense pathways activated in acd11 are salicylic acid (SA) dependent, but do not require intact jasmonic acid or ethylene signaling pathways. Light is required for PCD execution in acd11, as application of an SA-analog to SA-deficient acd11 induced death in the light, but not in the dark. Epistatic analysis showed that the SA-dependent pathways require two regulators of SA-mediated resistance responses, PAD4 and EDS1. Furthermore, acd11 PR1 gene expression, but not cell death, depends on the SA signal tranducer NPR1, suggesting that the npr1-1 mutation uncouples resistance responses and cell death in acd11. The acd11 phenotype is caused by deletion of the ACD11 gene encoding a protein homologous to a mammalian glycolipid transfer protein (GLTP). In contrast to GLTP, ACD11 accelerates the transfer of sphingosine, but not of glycosphingolipids, between membranes in vitro.

Glycerolipid transfer for the building of membranes in plant cells

“…The Arabidopsis ACD11 protein is involved in the cell death mechanism and, by contrast with the mammalian protein, it transfers only sphingosine [97]. No evidence was found of the GLTP involvement in galactolipid transfer in plants but because of some similarities of galactocerebroside to the glycosylglycerides, this hypothesis remains possible.…”

Glycolipid transfer protein: Clear structure and activity, but enigmatic function

“…These proteins have been isolated from different sources ranging from spinach chloroplasts to mammalian brain, liver and kidney (Brown et al, 1990;Sasaki, 1985Sasaki, , 1990. GLTP orthologs in fungi and plants were found to be involved in programmed cell death (Brodersen et al, 2002;Mattjus et al, 2003;Saupe et al, 1994) but their function in mammals is largely unknown. The activity of GLTP is preserved after expression in E. coli (Godi et al, 2004;Lin et al, 2000;Malinina et al, 2004;Rao et al, 2004) allowing for detailed structureefunction studies in vitro.…”

Maltose-binding protein switches programmed cell death in Nicotiana glutinosa leaf cells

“…Arabidopsis acd11 encoding a sphingosine transfer protein causes activation of PCD and defense [15]. sfd4/fab6 which encode a plastidic 6-desaturase have also been shown to potentiate cell death [16].…”