title: Degradation of long-chain base 1-phosphate (LCBP) in Arabidopsis: functional characterization of LCBP phosphatase involved in the dehydration stress response.
abstract: Sphingolipid metabolites, long-chain base 1-phosphates (LCBPs), are involved in ABA signaling pathways. The LCBPs synthesized by long-chain base kinase are dephosphorylated by LCBP phosphatase or degraded by LCBP lyase. Here we show that the At3g58490 gene encodes AtSPP1, a functional LCBP phosphatase. Transient expression of green fluorescent protein fusion in suspension-cultured Arabidopsis cells showed that AtSPP1 is localized in the endoplasmic reticulum. The level of dihydrosphingosine 1-phosphate was increased in loss-of-function mutants (spp1) compared with wild-type (WT) plants, suggesting a role of AtSPP1 in regulating LCBP levels. The rate of decrease in fresh weight of detached aerial parts was significantly slower in spp1 mutants than in WT plants. A stomatal closure bioassay showed that the stomata of spp1 mutants were more sensitive than the WT to ABA, suggesting that AtSPP1 is involved in guard cell signaling. However, spp1 mutants showed decreased sensitivity to ABA with respect to primary root growth but not to seed germination. The response to fumonisin B(1) did not differ between the WT and spp1 mutant. A significant decrease in AtDPL1 (LCBP lyase) transcripts in spp1 mutants was observed. We conclude that AtSPP1 is a functional LCBP phosphatase that may play a role in stomatal responses through LCBP-mediated ABA signaling.
authors: Department of Biology, Graduate School of Natural Science, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan.
authors: Noriko
authors: N
authors: Nakagawa
authors: Mai
authors: M
authors: Kato
authors: Yohei
authors: Y
authors: Takahashi
authors: Ken-Ichiro
authors: K
authors: Shimazaki
authors: Kentarao
authors: K
authors: Tamura
authors: Yoshihiko
authors: Y
authors: Tokuji
authors: Akio
authors: A
authors: Kihara
authors: Hiroyuki
authors: H
authors: Imai
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D000064:Acclimatization / Q000502:physiology*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D014644:Genetic Variation; D005838:Genotype; D009154:Mutation; D010710:Phosphates / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D035261:Plant Components, Aerial / Q000378:metabolism; D054046:Plant Stomata / Q000378:metabolism; D059748:Proteolysis; D015398:Signal Transduction; D013107:Sphingolipids / Q000378:metabolism; D013312:Stress, Physiological / Q000502:physiology*
chemical_list: D010710:Phosphates; D013107:Sphingolipids; D000040:Abscisic Acid; D010744:Phosphoric Monoester Hydrolases