Adaptive evolution has targeted the C-terminal domain of the RXLR effectors of plant pathogenic oomycetes
Adaptive evolution has targeted the C-terminal domain of the RXLR effectors of plant pathogenic oomycetes
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DOI：
10.1105/tpc.107.051037
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发表时间：
2007-08-01
期刊：
影响因子：
11.6
通讯作者：
Kamoun, Sophien
中科院分区：
文献类型：
--
作者：
Win, Joe;Morgan, William;Kamoun, Sophien
植物卵菌病原体在宿主细胞内传递效应蛋白，调节植物防御回路，使寄生定植成为可能。这些效应物由一个保守的基序定义，称为RXLR (Arg，任何氨基酸，Leu, Arg)，它位于信号肽的下游，并与宿主易位有关。由于RXLR效应物的表型延伸到植物细胞，它们的基因有望成为驱动病原体和宿主之间拮抗相互作用的进化力量的直接目标。我们利用大豆疫霉（Phytophthora sojae）、拉疫霉（Phytophthora ramorum）和寄生透明肉孢菌（Hyaloperonospora parasitica）三种植物卵霉菌病原菌的基因组草图序列，生成了RXLR效应基因的全基因组目录，并确定了这些基因在正选择作用下的程度。这些分析表明，相对于其他真核生物，RXLR序列在疫霉菌分泌组中被过度代表和位置受限。所研究的三种植物致病卵菌携带复杂多样的RXLR效应基因，这些基因经历了相对快速的生灭进化。我们获得了强有力的证据，证明在超过三分之二的RXLR效应物平行家族中存在正向选择。正选择主要作用于c端区域，这与RXLR效应物是模块化的观点一致，植物细胞内N端参与分泌和宿主易位，c端专门调节宿主防御。
Oomycete plant pathogens deliver effector proteins inside host cells to modulate plant defense circuitry and to enable parasitic colonization. These effectors are defined by a conserved motif, termed RXLR (for Arg, any amino acid, Leu, Arg), that is located downstream of the signal peptide and that has been implicated in host translocation. Because the phenotypes of RXLR effectors extend to plant cells, their genes are expected to be the direct target of the evolutionary forces that drive the antagonistic interplay between pathogen and host. We used the draft genome sequences of three oomycete plant pathogens, Phytophthora sojae, Phytophthora ramorum, and Hyaloperonospora parasitica, to generate genome-wide catalogs of RXLR effector genes and determine the extent to which these genes are under positive selection. These analyses revealed that the RXLR sequence is overrepresented and positionally constrained in the secretome of Phytophthora relative to other eukaryotes. The three examined plant pathogenic oomycetes carry complex and diverse sets of RXLR effector genes that have undergone relatively rapid birth and death evolution. We obtained robust evidence of positive selection in more than two-thirds of the examined paralog families of RXLR effectors. Positive selection has acted for the most part on the C-terminal region, consistent with the view that RXLR effectors are modular, with the N terminus involved in secretion and host translocation and the C-terminal domain dedicated to modulating host defenses inside plant cells.