大蒜半胱氨酸合成酶基因家族鉴定及表达分析

Identification and Gene Expression Pattern of Cysteine Synthases Gene Family in Garlic

大蒜含有丰富的含硫化合物,这些化合物均源于半胱氨酸,半胱氨酸合成酶在含硫化物的代谢中占据了重要地位。本研究通过大蒜的转录组数据库分析了118条注释为半胱氨酸合成酶的Unigene,从中找到9条具有全长的序列,使用生物信息学软件预测了其分子量、等电点、疏水性、稳定性系数、跨膜结构域、亚细胞定位,并对这些基因的蛋白结构域、Motif进行了预测,采用多重比较对这9个基因进行了相互比较,与植物中其他的半胱氨酸合成酶序列构建了系统进化树。结果表明,As CS6与As CS2X1在N端存在跨膜结构域,As CS26在N端存在低复杂度区域,其余半胱氨酸合成酶都仅有1个PALP结构域。MEME motif分析表明大多数大蒜半胱氨酸合成酶均有7个motif,As CS26缺少motif 4,As CS2X1缺少Motif 5。As CS2X1在序列中比其他半胱氨酸合成酶多出19个氨基酸残基,As CS2X1与其他半胱氨酸合成酶序列的一致性均小于0.26。系统进化树分析表明植物的半胱氨酸合成酶家族分为了6个亚家族,大蒜的9个半胱氨酸合成酶分布于其中的4组,As CS2X1所在第VI组与其他半胱氨酸合成酶的遗传距离较远,序列相似度低,与已知的PALP亚家族的成员关系也较远,可能是一类新的PALP亚家族成员。大多数半胱氨酸合成酶在根茎叶中均有表达,AsCS5、AsCS6在根中特异表达,AsCS26在茎中表达量高。

There were many kinds of sulfocompound in garlic,which were source of cysteine,so cysteine synthase owned the central place of sulfur metabolism in plant.9 full-length gene sequence was obtained from 118Unigene sequences annotated as cysteine synthase in transcriptome database of garlic.Then,their molecular weight,isoelectric point,hydropathicity,instability index,transmembrane domain,subsellular localization were predicted using bioinformatics software.The protein domains and motifs of 9 cysteine synthases were analysised by SMART and MEME.9 cysteine synthases were compared with each other using multiple comparisons and the phylogenetic tree was constructed with other cysteine synthase sequences in plants.The results showed that all the 9 cysteine synthases genes were correct and could be cloned.As CS6 and As CS2X1 had one transmembrane domain at the N-terminus,As CS26 had low-complexity regions at the N-terminus,others cysteine synthases had only one PALP domains.Most garlic cysteine synthases had 7 Motifs,but As CS26 lacks motif 4 and As CS2X1 lacks motif 5 in MEME motif analysis.As CS2X1 has extra 19 amino acid residues in the middle than other cysteine synthases,and the identity of As CS2X1 with other cysteine synthase sequences is less than 0.26.Phylogenetic tree analysis showed that the cysteine synthase family of plants was divided into 6 subfamilies,9 cysteine synthases of garlic were distributed in 4 of them,and group VI where As CS2X1 was located was genetically distant from other cysteine synthases,and was also far away from the members of other PALP subfamily gene,possibly was a new class of PALP subfamily members.Most cysteine synthases are expressed in root,stem and leaves,AsCS5 and AsCS6are specifically expressed in roots,and AsCS26 is expressed in stems abundant.