title: Arabidopsis Bax inhibitor-1 promotes sphingolipid synthesis during cold stress by interacting with ceramide-modifying enzymes.
abstract: Bax inhibitor-1 (BI-1) is a widely conserved cell death suppressor localized in the endoplasmic reticulum membrane. Our previous results revealed that Arabidopsis BI-1 (AtBI-1) interacts with not only Arabidopsis cytochrome b 5 (Cb5), an electron transfer protein, but also a Cb5-like domain (Cb5LD)-containing protein, Saccharomyces cerevisiae fatty acid 2-hydroxylase 1, which 2-hydroxylates sphingolipid fatty acids. We have now found that AtBI-1 binds Arabidopsis sphingolipid Δ8 long-chain base (LCB) desaturases AtSLD1 and AtSLD2, which are Cb5LD-containing proteins. The expression of both AtBI-1 and AtSLD1 was increased by cold exposure. However, different phenotypes were observed in response to cold treatment between an atbi-1 mutant and a sld1sld2 double mutant. To elucidate the reasons behind the difference, we analyzed sphingolipids and found that unsaturated LCBs in atbi-1 were not altered compared to wild type, whereas almost all LCBs in sld1sld2 were saturated, suggesting that AtBI-1 may not be necessary for the desaturation of LCBs. On the other hand, the sphingolipid content in wild type increased in response to low temperature, whereas total sphingolipid levels in atbi-1 were unaltered. In addition, the ceramide-modifying enzymes AtFAH1, sphingolipid base hydroxylase 2 (AtSBH2), acyl lipid desaturase 2 (AtADS2) and AtSLD1 were highly expressed under cold stress, and all are likely to be related to AtBI-1 function. These findings suggest that AtBI-1 contributes to synthesis of sphingolipids during cold stress by interacting with AtSLD1, AtFAH1, AtSBH2 and AtADS2.
authors.affiliation: Graduate School of Biological Science, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, 630-0192, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Nagano
authors.forename: Toshiki
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Iwabuchi
authors.forename: Akari
authors.initials: A
authors.lastname: Nakasone
authors.forename: Ko
authors.initials: K
authors.lastname: Shimamoto
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Uchimiya
authors.forename: Maki
authors.initials: M
authors.lastname: Kawai-Yamada
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism; D003080:Cold Temperature; D005227:Fatty Acids / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010088:Oxidoreductases; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013107:Sphingolipids / Q000032:analysis / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: C491862:ATBI-1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002518:Ceramides; D005227:Fatty Acids; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; C000592613:SLP1 protein, Arabidopsis; C000592614:SLP2 protein, Arabidopsis; D013107:Sphingolipids; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C575859:fatty acid 2-hydroxylase 1, Arabidopsis; C115532:sphingolipid desaturase