Table 2.

Characterized Arabidopsis genes implicated in sphingolipid-perturbation induced PCD related to defense.

Gene symbol	Gene ID	Gene product	PCD-related phenotypes	Possible mechanisms involved	Reference
LCB1 (FBR11)	At4g36480	Subunit of serine palmitoyltransferase (SPT)	The fbr11-1 knockdown mutant is less sensitive to FB1-induced	Low levels of LCBs	Chen et al. (2006), Shi et al. (2007)
LCB2a	At5g23670	Subunit 2 of SPT	The lcb2a knockout mutant is less sensitive to FB1-induced PCD	Low levels of LCBs	Saucedo-Garcia et al. (2011b)
SBH1/SBH2	At1g14290/At1g69640	Sphingolipid-C4-hydroxylase	The double mutant is dwarfed and with PCD spots	Higher levels of C16-sphingolipids and lower levels of VLCFA-sphingolipids, and/or lack of trihydroxy LCBs	Chen et al. (2008)
SphK1/SphK2	At4g21540/At2g46090	sphingosine kinase	The sphk1 knockout mutant is less sensitive to ABA; Inhibition of the enzymatic activity makes cells more sensitive to LCB-induced PCD	Increase in LCBs/LCB-Ps ratio	Coursol et al. (2003), Worrall et al. (2008), Alden et al. (2011), Guo et al. (2011)
AtDPL1	At1g27980	LCB phosphate lyase	The knockout mutant has increased sensitivity to FB1-induced PCD	Increase in LCBs/LCB-Ps ratio	Tsegaye et al. (2007)
LOH1	At3g25540	Ceramide synthase (using VLCFA)	The loh1 knockout mutant shows PCD associated with PR gene expression	Accumulation of LCBs and C16-ceramides, and/or reduction in VLCFA-ceramides	Markham et al. (2011), Ternes et al. (2011)
LOH2	At3g19260	Ceramide synthase (using C16 FA)	Reduction in C16-ceramides; No obvious phenotype detected so far	NA	Markham et al. (2011), Ternes et al. (2011)
LOH3	At1g13580	Ceramide synthase (using VLCFA)	The loh1/loh3 double knockdown mutant has accumulation of LCBs and C16-ceramides, but reduction in VLCFA-ceramides	Mimicking the effect of FB1 treatment	Markham et al. (2011), Ternes et al. (2011)
CERK (ACD5)	At5g51290	Ceramide kinase	The acd5 knockout mutant develops SA-dependent PCD, and is more susceptible to P. syringae but more resistant to powdery mildew	Accumulation of ceramides	Liang et al. (2003), Wang et al. (2008)
FAH1/FAH2	At2g34770/At4g20870	Fatty acyl α-hydroxylase	AtFAHs are required for AtBI-mediated suppression of PCD in mutant yeast	Complementation of yeast fah mutant	Nagano et al. (2009)
IPCS2 (ERH1)	At2g37940	Inositol-phosphoryl-ceramide synthase	The erh1 knockout mutant develops SA-dependent PCD in plants expressing RPW8	Accumulation of ceramides with a trihydroxy LCB and a non-hydroxylated C16 fatty acid	Wang et al. (2008)
ACD11	At2g34690	Sphingosine transfer protein	The acd11-knockout mutant develops SA-dependent PCD	Failure in sphingolipid transport?	Brodersen et al. (2002), Petersen et al. (2008)
MIPS1	At4g39800	Myo-inositol 1-phosphate synthase	The mips1 knockout mutant develops PCD associated with defense	Ceramide accumulation due to deficiency in phosphatidylinositol as substrate for IPCSs	Meng et al. (2009), Donahue et al. (2010)
MPK6	At2g43790	MAP kinase	The mpk6 knock out mutant is less sensitive to FB1 or free LCB (d18:0) induced PCD	Defective in LCB-triggered MAPK signaling engaged in LCB-triggered PCD	Saucedo-Garcia et al. (2011b)
Myb30	At3G28910	Transcription factor	Myb30 positively regulates HR and defense	Activation of genes encoding components of acyl-CoA elongase complex required for VLCFA synthesis	Raffaele et al. (2008), Canonne et al. (2011)