The essential nature of sphingolipids in plants as revealed by the functional identification and characterization of the Arabidopsis LCB1 subunit of serine palmitoyltransferase.
Serine palmitoyltransferase (SPT) catalyzes the first step of sphingolipid biosynthesis. In yeast and mammalian cells, SPT is a heterodimer that consists of LCB1 and LCB2 subunits, which together form the active site of this enzyme. We show that the predicted gene for Arabidopsis thaliana LCB1 encodes a genuine subunit of SPT that rescues the sphingolipid long-chain base auxotrophy of Saccharomyces cerevisiae SPT mutants when coexpressed with Arabidopsis LCB2. In addition, homozygous T-DNA insertion mutants for At LCB1 were not recoverable, but viability was restored by complementation with the wild-type At LCB1 gene. Furthermore, partial RNA interference (RNAi) suppression of At LCB1 expression was accompanied by a marked reduction in plant size that resulted primarily from reduced cell expansion. Sphingolipid content on a weight basis was not changed significantly in the RNAi suppression plants, suggesting that plants compensate for the downregulation of sphingolipid synthesis by reduced growth. At LCB1 RNAi suppression plants also displayed altered leaf morphology and increases in relative amounts of saturated sphingolipid long-chain bases. These results demonstrate that plant SPT is a heteromeric enzyme and that sphingolipids are essential components of plant cells and contribute to growth and development.
Chen
Ming
M
Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA.
Han
Gongshe
G
Dietrich
Charles R
CR
Dunn
Teresa M
TM
Cahoon
Edgar B
EB
D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000033:anatomy & histology / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D006801:Humans; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000166:cytology / Q000201:enzymology; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry; D012639:Seeds / Q000166:cytology / Q000201:enzymology; D017385:Sequence Homology; D051102:Serine C-Palmitoyltransferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013107:Sphingolipids / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D013489:Suppression, Genetic
D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D021122:Protein Subunits; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids; C036483:T-DNA; C518504:LCB1 protein, Arabidopsis; C495086:LCB1 protein, S cerevisiae; D051102:Serine C-Palmitoyltransferase