Ancient origin of elicitin gene clusters in Phytophthora genomes
Ancient origin of elicitin gene clusters in Phytophthora genomes
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DOI：
10.1093/molbev/msj039
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发表时间：
2006-02-01
影响因子：
10.7
通讯作者：
Govers, F
中科院分区：
文献类型：
--
作者：
Jiang, RHY;Tyler, BM;Govers, F
疫霉属（Phytophthora）属于真核层枝菌属（stratificile）中的卵菌纲，由超过65个种组成，这些种都是广泛的双子叶植物上的破坏性植物病原体。疫霉菌产生激发素（ELI），一组引起烟草过敏反应的胞外激发蛋白。数据库挖掘揭示了几类新的激发素样（ELL）序列，具有不同的激发素结构域的致病疫霉，大豆疫霉，芸苔疫霉，和多枝疫霉。ELI和ELL显示为疫霉属和腐霉属物种所特有。它们普遍存在于疫霉属物种中，属于疫霉属中最高度保守和复杂的蛋白质家族之一。系统发育构建与elicitin结构域来自156 ELI和ELLs显示，大多数的多样化的家庭成员存在之前，疫霉物种从一个共同的祖先分歧。对17个ELI和ELL进化枝进行了分化选择和纯化选择的判别分析，结果表明，所有17个ELI和ELL进化枝均处于纯化选择状态。在高度相似的ELI组中，没有证据表明正选择的氨基酸表明纯化选择有助于这种多样性蛋白质家族的继续存在。特征半胱氨酸间隔模式被发现为每个系统发育分支。除了典型的进化枝ELI-1，ELI和ELL具有可变长度的C-末端结构域，其中许多具有高的苏氨酸、丝氨酸或脯氨酸含量，表明与细胞壁的关联。此外，一些ELI和ELL具有预测的糖基磷脂酰肌醇位点，表明C-末端结构域锚定至细胞膜。属于不同进化枝的eli和ell基因在基因组中聚集。总的来说，eli和ell基因在不同的生活史阶段以不同的水平表达，但共享同一系统进化枝的基因似乎具有相似的表达模式。
The genus Phytophthora belongs to the oomycetes in the eukaryotic stramenopile lineage and is comprised of over 65 species that are all destructive plant pathogens on a wide range of dicotyledons. Phytophthora produces elicitins (ELIs), a group of extracellular elicitor proteins that cause a hypersensitive response in tobacco. Database mining revealed several new classes of elicitin-like (ELL) sequences with diverse elicitin domains in Phytophthora infestans, Phytophthora sojae, Phytophthora brassicae, and Phytophthora ramorum. ELIs and ELLs were shown to be unique to Phytophthora and Pythium species. They are ubiquitous among Phytophthora species and belong to one of the most highly conserved and complex protein families in the Phytophthora genus. Phylogeny construction with elicitin domains derived from 156 ELIs and ELLs showed that most of the diversified family members existed prior to divergence of Phytophthora species from a common ancestor. Analysis to discriminate diversifying and purifying selection showed that all 17 ELI and ELL clades are under purifying selection. Within highly similar ELI groups there was no evidence for positively selected amino acids suggesting that purifying selection contributes to the continued existence of this diverse protein family. Characteristic cysteine spacing patterns were found for each phylogenetic clade. Except for the canonical clade ELI-1, ELIs and ELLs possess C-terminal domains of variable length, many of which have a high threonine, serine, or proline content suggesting an association with the cell wall. In addition, some ELIs and ELLs have a predicted glycosylphosphatidylinositol site suggesting anchoring of the C-terminal domain to the cell membrane. The eli and ell genes belonging to different clades are clustered in the genomes. Overall, eli and ell genes are expressed at different levels and in different life cycle stages but those sharing the same phylogenetic clade appear to have similar expression patterns.