<i>Arabidopsis</i>56–Amino Acid Serine Palmitoyltransferase-Interacting Proteins Stimulate Sphingolipid Synthesis, Are Essential, and Affect Mycotoxin Sensitivity

Kimberlin, Athen; Majumder, Saurav; Han, Gongshe; Chen, Ming; Cahoon, Rebecca E.; Stone, Julie M.; Dunn, Teresa M.; Cahoon, Edgar B.

doi:10.1105/tpc.113.116145

Cited by 59 publications

(106 citation statements)

References 59 publications

(117 reference statements)

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“…Sphingolipidomic profiling revealed little quantitative difference between amounts of sphingolipids in Col-0 and AtORM overexpression lines and virtually no difference in amounts of sphingolipids between AtORM overexpression lines with or without a growth phenotype, especially in the GIPC and GlcCer classes (Supplemental Figs. S3-S6), similar to previous findings with AtssSPT overexpression or RNAi suppression (Kimberlin et al, 2013). It was notable that concentrations of the LCB t18:0 were elevated in ceramide and GIPC molecular species in dwarfed AtORM1 and AtORM2 plants compared with Col-0 control plants ( Supplemental Fig.…”

Section: Overexpression Of Atorm1 and Atorm2 Results In Dwarfed Growthsupporting

confidence: 79%

“…4, C and F). These results suggest that a threshold of AtORM1 and AtORM2 protein levels can be reached to suppress SPT activity sufficiently to reduce growth, as observed previously for AtLCB1 RNAi suppression (Chen et al, 2006) and reduced AtssSPTa expression (Kimberlin et al, 2013). Sphingolipidomic profiling revealed little quantitative difference between amounts of sphingolipids in Col-0 and AtORM overexpression lines and virtually no difference in amounts of sphingolipids between AtORM overexpression lines with or without a growth phenotype, especially in the GIPC and GlcCer classes (Supplemental Figs.…”

Section: Overexpression Of Atorm1 and Atorm2 Results In Dwarfed Growthsupporting

confidence: 51%

“…Tagged ORM1 and ORM2 colocalized with the ER marker mCherry-HDEL (Fig. 3,C and F), consistent with the known ER localization of AtLCB1, AtLCB2a/ 2b, and AtssSPTa/b (Chen et al, 2006;Dietrich et al, 2008;Teng et al, 2008;Kimberlin et al, 2013), but also were detected in other subcellular locations, including the cytosol (Fig. 3, A, C, D, and F).…”

Section: Two Functional Homologs Of Mammalian Ormdlssupporting

confidence: 63%

“…Research to date has shown that SPT is regulated primarily by posttranslational mechanisms involving physical interactions with noncatalytic, membrane-associated proteins that confer positive and negative regulation of SPT activity (Han et al, 2009Breslow et al, 2010). These proteins include a 56-amino acid small subunit of SPT (ssSPT) in Arabidopsis, which was recently shown to stimulate SPT activity and to be essential for generating sufficient amounts of sphingolipids for pollen and sporophytic cell viability (Kimberlin et al, 2013).…”

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confidence: 99%

“…In plants, the maintenance of sphingolipid homeostasis is vital to ensure sufficient sphingolipids for growth (Chen et al, 2006;Kimberlin et al, 2013) while restricting the accumulation of PCD-inducing ceramides and LCBs until required for processes such as the pathogen-triggered hypersensitive response. Serine palmitoyltransferase (SPT), which catalyzes the first step in LCB synthesis, is generally believed to be the primary control point for sphingolipid homeostasis (Hanada, 2003).…”

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confidence: 99%

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ORM Expression Alters Sphingolipid Homeostasis and Differentially Affects Ceramide Synthase Activities

et al. 2016

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Sphingolipid synthesis is tightly regulated in eukaryotes. This regulation in plants ensures sufficient sphingolipids to support growth while limiting the accumulation of sphingolipid metabolites that induce programmed cell death. Serine palmitoyltransferase (SPT) catalyzes the first step in sphingolipid biosynthesis and is considered the primary sphingolipid homeostatic regulatory point. In this report, Arabidopsis (Arabidopsis thaliana) putative SPT regulatory proteins, orosomucoidlike proteins AtORM1 and AtORM2, were found to interact physically with Arabidopsis SPT and to suppress SPT activity when coexpressed with Arabidopsis SPT subunits long-chain base1 (LCB1) and LCB2 and the small subunit of SPT in a yeast (Saccharomyces cerevisiae) SPT-deficient mutant. Consistent with a role in SPT suppression, AtORM1 and AtORM2 overexpression lines displayed increased resistance to the programmed cell death-inducing mycotoxin fumonisin B 1 , with an accompanying reduced accumulation of LCBs and C16 fatty acid-containing ceramides relative to wild-type plants. Conversely, RNA interference (RNAi) suppression lines of AtORM1 and AtORM2 displayed increased sensitivity to fumonisin B 1 and an accompanying strong increase in LCBs and C16 fatty acid-containing ceramides relative to wild-type plants. Overexpression lines also were found to have reduced activity of the class I ceramide synthase that uses C16 fatty acid acyl-coenzyme A and dihydroxy LCB substrates but increased activity of class II ceramide synthases that use very-long-chain fatty acyl-coenzyme A and trihydroxy LCB substrates. RNAi suppression lines, in contrast, displayed increased class I ceramide synthase activity but reduced class II ceramide synthase activity. These findings indicate that ORM mediation of SPT activity differentially regulates functionally distinct ceramide synthase activities as part of a broader sphingolipid homeostatic regulatory network.

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Section: Overexpression Of Atorm1 and Atorm2 Results In Dwarfed Growthsupporting

confidence: 79%

Section: Overexpression Of Atorm1 and Atorm2 Results In Dwarfed Growthsupporting

confidence: 51%

Section: Two Functional Homologs Of Mammalian Ormdlssupporting

confidence: 63%

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confidence: 99%

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confidence: 99%

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ORM Expression Alters Sphingolipid Homeostasis and Differentially Affects Ceramide Synthase Activities

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Plant Sphingolipids

Belton¹,

Ng²

2020

Encyclopedia of Life Sciences

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Sphingolipids, a class of amino alcohol‐based lipids, are major eukaryotic lipids, and they have also been found in some prokaryotes. Since the discovery of sphingolipids by Johann Ludwig Thudichum in 1874, this class of lipids is now less enigmatic, and to date, we have a much better understanding of how they are metabolised, their structural diversity and the roles they play in regulating eukaryotic cellular processes and physiology. Our understanding of the functional roles of sphingolipids in cells has come largely from studies using mammalian cells and yeast. However, in the past 20 years, we have made great strides in our understanding of plant sphingolipid metabolism, structure and function. Readers are encouraged to refer to the relevant literature for further detailed information. Key Concepts Sphingolipids are major eukaryotic lipids, and they have been shown to be important in membrane organisation, as well as playing key roles in regulating cellular physiology. The de novo biosynthesis of sphingolipids in all eukaryotes begins in the endoplasmic reticulum (ER) and is catalysed by the pyridoxal 5′‐phosphate (PLP)‐dependent serine palmitoyltransferase (SPT), resulting in the formation of long‐chain bases (LCBs). The LCBs can undergo further metabolism to form more complex sphingolipids, such as ceramides, glucosylceramides and glycosyl inositolphosphoceramides (GIPCs). In addition to the de novo pathway, all eukaryotes also possess the salvage pathway whereby LCBs are recovered from ceramides, and key to this salvage pathway is a class of enzymes known as ceramidases. Plant sphingolipids have been shown to function in membrane organisation, abiotic and biotic stress responses, regulation of developmental processes and plant physiology.

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