title: Cloning and expression analysis of squalene synthase, a key enzyme involved in antifungal steroidal glycoalkaloids biosynthesis from Solanum nigrum.
abstract: Steroidal glycoalkaloids (SGAs) are a family of nitrogenous secondary metabolites produced in solanaceous plants. In our present study, γ-solamargine and its aglycone solasodine from Solanum nigrum were found to inhibit hyphae formation of Fusarium oxysporum. As phytoalexins, the formation of SGAs was significantly increased in the plants when infected with the spore of F. oxysporum. In order to understand this inducible defense mechanism, the rate-limiting enzyme squalene synthase in the biosynthesis process of SGAs was investigated well. A full-length cDNA encoding squalene synthase was isolated from S. nigrum (the squalene synthase in S. nigrum was designated as SnSS). The full-length cDNA of SnSS was 1,765 bp and contained a 1,236 bp open reading frame (ORF) encoding a polypeptide of 411 amino acids. Bioinformatic analysis revealed that the deduced SnSS protein had a high similarity with other plant squalene synthases. Real-time RT-PCR analysis showed that SnSS was expressed constitutively in all tested tissues, with the highest expression in stems. After treatment with the spore of F. oxysporum, the mRNA level of SnSS was significantly increased in the infected plants in accordance with the change of SGAs.
authors.affiliation: School of Pharmaceutical Sciences, Shandong University, Ji'nan, Shandong, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Sun
authors.forename: Y
authors.initials: Y
authors.lastname: Zhao
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: H X
authors.initials: HX
authors.lastname: Lou
authors.forename: A X
authors.initials: AX
authors.lastname: Cheng
mesh_terms: D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000378:metabolism*; D003001:Cloning, Molecular; D019295:Computational Biology; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000235:genetics / Q000378:metabolism*; D005670:Fusarium / Q000187:drug effects / Q000254:growth & development; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D025301:Hyphae / Q000187:drug effects; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020539:Sequence Analysis, Protein; D012991:Solanaceous Alkaloids / Q000096:biosynthesis*; D032324:Solanum nigrum / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D015854:Up-Regulation
chemical_list: D000935:Antifungal Agents; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D012991:Solanaceous Alkaloids; D013186:Farnesyl-Diphosphate Farnesyltransferase; C012037:solasodine