A Recent Expansion of the RXLR Effector Gene Avrblb2 Is Maintained in Global Populations of Phytophthora infestans Indicating Different Contributions to Virulence
A Recent Expansion of the RXLR Effector Gene Avrblb2 Is Maintained in Global Populations of Phytophthora infestans Indicating Different Contributions to Virulence
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DOI：
10.1094/mpmi-12-14-0393-r
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发表时间：
2015-08-01
影响因子：
3.5
通讯作者：
Kamoun, Sophien
中科院分区：
文献类型：
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作者：
Oliva, Ricardo F.;Cano, Liliana M.;Kamoun, Sophien
将编码具有广谱识别能力的免疫受体的抗病（R）基因渗入栽培马铃薯中似乎是实现对由卵菌病原体致病疫霉（Phytophthora infestans）引起的晚疫病进行可持续管理的最有前途的方法。根据马铃薯病害初步试验，来自 Solanumbulbo-castanum 的 Rpi-blb2 显示出在农业中的巨大应用潜力。 Rpi-blb2 通过识别转位到植物细胞内的致病疫霉无毒效应蛋白 AVRblb2 来赋予免疫力。该效应器属于RXLR类效应器，处于强正选择状态。结构功能分析揭示了 AVRblb2 效应子中的一个关键多态性氨基酸（第 69 位），该氨基酸对于 Rpi-blb2 的激活至关重要。在这项研究中，我们重建了 Avrblb2 基因家族的进化史，并进一步表征了其在全球人群中的遗传结构。我们的数据表明，Avrblb2 在致病疫霉的推定祖先物种中进化为单拷贝基因，并且最近在疫霉属中扩展。感染茄科宿主。因此，致病疫霉中至少出现了四种 AVRblb2 变体。这些变体之一在第 69 位具有 Phe 残基，可逃避同源抗性基因的识别。令人惊讶的是，所有 Avrblb2 变体都保留在病原体群体中。这表明保存 AVRblb2 的重复版本对病原体具有潜在的好处，可能是因为这些变体可能对多样化茄科宿主环境中的病原体适应性有不同的贡献。
The introgression of disease resistance (R) genes encoding immunoreceptors with broad-spectrum recognition into cultivated potato appears to be the most promising approach to achieve sustainable management of late blight caused by the oomycete pathogen Phytophthora infestans. Rpi-blb2 from Solanum bulbo-castanum shows great potential for use in agriculture based on preliminary potato disease trials. Rpi-blb2 confers immunity by recognizing the P. infestans avirulence effector protein AVRblb2 after it is translocated inside the plant cell. This effector belongs to the RXLR class of effectors and is under strong positive selection. Structure-function analyses revealed a key polymorphic amino acid (position 69) in AVRblb2 effector that is critical for activation of Rpi-blb2. In this study, we reconstructed the evolutionary history of the Avrblb2 gene family and further characterized its genetic structure in worldwide populations. Our data indicate that Avrblb2 evolved as a single-copy gene in a putative ancestral species of P. infestans and has recently expanded in the Phytophthora spp. that infect solanaceous hosts. As a consequence, at least four variants of AVRblb2 arose in P. infestans. One of these variants, with a Phe residue at position 69, evades recognition by the cognate resistance gene. Surprisingly, all Avrblb2 variants are maintained in pathogen populations. This suggests a potential benefit for the pathogen in preserving duplicated versions of AVRblb2, possibly because the variants may have different contributions to pathogen fitness in a diversified solanaceous host environment.