Effector gene reshuffling involves dispensable mini-chromosomes in the wheat blast fungus
Effector gene reshuffling involves dispensable mini-chromosomes in the wheat blast fungus
复制标题
DOI：
10.1371/journal.pgen.1008272
复制
发表时间：
2019-09-01
期刊：
影响因子：
4.5
通讯作者：
Liu, Sanzhen
中科院分区：
文献类型：
--
作者：
Peng, Zhao;Oliveira-Garcia, Ely;Liu, Sanzhen
作者总结：事实证明，小麦上新出现的稻瘟病比古老的、仍然存在问题的稻瘟病更难控制。利用发病后不久分离的菌株鉴定出的潜在小麦抗性不再有效地控制最近从南美洲和南亚小麦上分离的侵略性田间菌株。我们构建了一个具有侵略性的、最近分离的小麦稻瘟菌菌株的高质量组装，以及第一个组装的小麦和水稻稻瘟病病原菌的微型染色体基因组序列。我们报道，最近的小麦病原菌可以包含一个或两个高度可变的可有可无的小染色体，每个小染色体都含有真菌效应基因和其他序列的融合，这些序列在不可或缺的核心染色体末端复制或缺失。在水稻病原菌的不同核心染色体上发现了经过充分研究的效应子，它们并排出现在小麦病原菌的小染色体上。水稻病原菌通常通过删除触发效应基因来克服已部署的抗性基因。我们认为，小麦稻瘟病菌快速进化的富含效应器的区段是核心染色体末端和可移动的小染色体的组合，这些染色体很容易从单个菌株中丢失。因此，在小染色体上定位效应子将加速病原菌在田间的适应。新出现的小麦稻瘟病严重威胁着全球小麦生产。小麦稻瘟病是由引起稻瘟病的真菌的一种独特的、异常多样化的谱系引起的。通过对一个最新的野外分离株进行测序，我们报告了一个参考基因组，它包括7条核心染色体和微染色体序列，这些微染色体序列含有通常在其他菌株的核心染色体末端发现的效应基因。在早期的田间菌株中没有观察到微小染色体，来自另一个菌株的至少两个染色体分别包含不同的效应基因和核心染色体末端序列。小染色体富含最常出现在核心染色体末端的转座子。此外，微小染色体中的转座子缺乏通过重复诱导点(RIP)突变基因组防御而失活的特征特征。我们的结果总体上表明，小麦病原菌基因组中非必需的小染色体和核心染色体经历了不同的进化轨迹，而小染色体和核心染色体末端作为一个可移动的、快速进化的效应室耦合在一起。
Author summary The emerging blast disease on wheat is proving even harder to control than the ancient, still-problematic rice blast disease. Potential wheat resistance identified using strains isolated soon after disease emergence are no longer effective in controlling recent aggressive field isolates from wheat in South America and South Asia. We construct a high-quality assembly of an aggressive, recently-isolated wheat blast fungal strain and the first assembled mini-chromosome genome sequence of wheat and rice blast pathogens. We report that recent wheat pathogens can contain one or two highly-variable dispensable mini-chromosomes, each with an amalgamation of fungal effector genes and other sequences that are duplicated or absent from indispensable core chromosome ends. Well-studied effectors found on different core chromosomes in rice pathogens appear side-by-side in wheat pathogen mini-chromosomes. The rice pathogen often overcomes deployed resistance genes by deleting triggering effector genes. We propose that the fast-evolving effector-rich compartment of the wheat blast fungus is a combination of core chromosome ends and mobile mini-chromosomes that are easily lost from individual strains. Localization of effectors on mini-chromosomes would therefore accelerate pathogen adaptation in the field.Newly emerged wheat blast disease is a serious threat to global wheat production. Wheat blast is caused by a distinct, exceptionally diverse lineage of the fungus causing rice blast disease. Through sequencing a recent field isolate, we report a reference genome that includes seven core chromosomes and mini-chromosome sequences that harbor effector genes normally found on ends of core chromosomes in other strains. No mini-chromosomes were observed in an early field strain, and at least two from another isolate each contain different effector genes and core chromosome end sequences. The mini-chromosome is enriched in transposons occurring most frequently at core chromosome ends. Additionally, transposons in mini-chromosomes lack the characteristic signature for inactivation by repeat-induced point (RIP) mutation genome defenses. Our results, collectively, indicate that dispensable mini-chromosomes and core chromosomes undergo divergent evolutionary trajectories, and mini-chromosomes and core chromosome ends are coupled as a mobile, fast-evolving effector compartment in the wheat pathogen genome.