条斑紫菜SAMS基因克隆与生物信息学分析

干旱、高盐和低温是限制植物生长和农作物产量的主要逆境因子。S-腺苷甲硫氨酸合成酶（S-adenosylmethionine synthetase，SAMS）与植物抗逆境密切相关，而且超表达SAMS的转基因植物具有更高的抗干旱、高盐和低温能力。进行条斑紫菜（Porphyra yezoensis）S-腺苷甲硫氨酸合成酶基因（PySAMS）cDNA的克隆及序列特征分析。首先利用电子克隆技术得到基因相关的contig，预测全长并设计引物，最后利用RT-PCR技术成功克隆了PySAMS的cDNA序列（GenBank accession：FJ404748）。该cDNA序列含有长1155nt的完整ORF，编码蛋白（PySAMS）分子量41.8kDa，长384AA。PySAMS与盘基网柄菌（Dictyostelium discoideum）、莱茵衣藻（Chlamydomonas reinhardtii）、拟南芥（Arabidopsis thaliana）和水稻（Oryza sativa）等多种生物的SAMS具有较高的序列一致性，含有与SAMS酶活性密切相关的氨基酸残基和保守序列，与人（Homo sapiens）和大肠杆菌（Escherichia coli）的SAMS具有高度相似的三维结构。所以PySAMS与其它生物的SAMS一样，在条斑紫菜的抗逆过程中发挥重要作用。研究PySAMS有助于阐明条斑紫菜耐受非生物胁迫的作用机理，有助于获得高抗逆转基因植物。

cDNA Cloning and Bioinformatic Analysis of SAMS Gene from Porphyra yezoensis

Abstract Drought, salinity and low temperature are the most abiotic stresses that make agriculture production reduction. The S-Adenosylmethionine synthetase (SAMS) gene (SAMS) is closely connected to tolerance to abiotic stresses. Furthermore, SAMS-overexpressing plant can be more tolerant to drought, salinity and low temperature. So investigation of SAMS is important to illustrate mechanism of tolerance to abiotic stresses, and to improve transgenic plant resistance through biotechnology. Isolation and characterization of cDNA of Porphyra yezoensis S-Adenosylmethionine synthetase gene (PySAMS) was reported. SAMS from other organisms was used as a probe to search the P. yezoensis dbEST. ESTs showing great similarity to CSase were assembled into contig. According to the open reading frame of contig, the primers were designed. Total RNA was isolated from thallus of P. yezoensis. And the cDNA sequence (GenBank accession: FJ404748) of PySAMS was isolated successfully through experiment of RT-PCR. The cDNA contains an 1155nt of continuous complete open reading frame (ORF) encoding a polypeptide of 384 amino acids with a calculated molecular mass of 41.8kDa. Sequence comparison of the PySAMS reveals high amino acid sequence identity with SAMS from other organism, such as Dictyostelium discoideum, Chlamydomonas reinhardtii, Arabidopsis thaliana and Oryza sativa.PySAMS contains conserved amino acids residue and sequences motifs closely related to function of SAMS enzyme, and possess highly similar tertiary structure with human SAMS. So like other SAMS, PySAMS plays an important role in tolerance to abiotic stresses in P. yezoensis, and is a key enzyme of cell activity.