Sphingolipid base modifying enzymes in sunflower (Helianthus annuus): cloning and characterization of a C4-hydroxylase gene and a new paralogous Δ8-desaturase gene.
Sphingolipids are components of plant cell membranes that participate in the regulation of important physiological processes. Unlike their animal counterparts, plant sphingolipids are characterized by high levels of base C4-hydroxylation. Moreover, desaturation at the Δ8 position predominates over the Δ4 desaturation typically found in animal sphingolipids. These modifications are due to the action of C4-hydroxylases and Δ8-long chain base desaturases, and they are important for complex sphingolipids finally becoming functional. The long chain bases of sunflower sphingolipids have high levels of hydroxylated and unsaturated moieties. Here, a C4-long chain base hydroxylase was functionally characterized in sunflower plant, an enzyme that could complement the sur2Δ mutation when heterologously expressed in this yeast mutant deficient in hydroxylation. This hydroxylase was ubiquitously expressed in sunflower, with the highest levels found in the developing cotyledons. In addition, we identified a new Δ8-long base chain desaturase gene that displays strong homology to a previously reported desaturase gene. This desaturase was also expressed in yeast and was able to change the long chain base composition of the transformed host. We studied the expression of this desaturase and compared it with that of the other isoform described in sunflower. The desaturase form studied in this paper displayed higher expression levels in developing seeds.
Instituto de la Grasa (CSIC), Av. Padre García Tejero 4, E-41012 Sevilla, Spain.
Antonio J
AJ
Moreno-Pérez
Enrique
E
Martínez-Force
Rafael
R
Garcés
Joaquín J
JJ
Salas
D000595:Amino Acid Sequence; D018548:Cotyledon / Q000201:enzymology / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D006368:Helianthus / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics; D018547:Plant Stems / Q000201:enzymology / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013107:Sphingolipids / Q000032:analysis / Q000378:metabolism*
D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C109313:SUR2 protein, S cerevisiae; C115532:sphingolipid desaturase