A guardian of grasses: Specific origin and conservation of a unique disease-resistance gene in the grass lineage
A guardian of grasses: Specific origin and conservation of a unique disease-resistance gene in the grass lineage
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DOI：
10.1073/pnas.0711406105
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发表时间：
2008-02
期刊：
影响因子：
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通讯作者：
A. Sindhu;Satya Chintamanani;Amanda S. Brandt;M. Zanis;S. Scofield;G. Johal
中科院分区：
文献类型：
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作者：
A. Sindhu;Satya Chintamanani;Amanda S. Brandt;M. Zanis;S. Scofield;G. Johal
玉米 Hm1 基因可针对由炭黑小种 1 (CCR1) 引起的致命叶枯病和耳霉病提供保护。尽管它是第一个被克隆的抗病 (DR) 基因，但它仍然是一个新鲜事物，因为 Hm1 不像大多数 DR 基因那样参与植物识别和响应系统，而是直接解除病原体的武装。它通过编码一种 NADPH 依赖性还原酶来实现这一点，该酶的功能是灭活碳长蠕孢菌 (HC) 毒素，这是一种含有环氧化物的环状四肽，是病原体产生的一种关键毒力因子，可在玉米中定殖。尽管 CCR1 严格来说是玉米的病原体，但 Hm1 的直系同源物和 HC 毒素还原酶活性存在于禾本科植物中，表明这种 DR 性状在植物中具有古老且进化上保守的作用。在这里，我们通过证明其参与大麦对 CCR1 的非宿主抗性来提供这种作用的证据。 Hm1 同源物表达被沉默的大麦叶子变得容易受到 CCR1 的感染，但前提是病原体能够产生 HC 毒素。系统发育分析表明，Hm1 在禾本科谱系的早期专门进化。鉴于 CCR1 杀死玉米的毁灭性能力，这些发现意味着，如果 Hm1 没有出现，禾本科植物的进化和/或地理分布可能会受到限制。
The maize Hm1 gene provides protection against a lethal leaf blight and ear mold disease caused by Cochliobolus carbonum race 1 (CCR1). Although it was the first disease-resistance (DR) gene to be cloned, it remains a novelty because, instead of participating in the plant recognition and response system as most DR genes do, Hm1 disarms the pathogen directly. It does so by encoding an NADPH-dependent reductase, whose function is to inactivate Helminthosporium carbonum (HC) toxin, an epoxide-containing cyclic tetrapeptide, which the pathogen produces as a key virulence factor to colonize maize. Although CCR1 is strictly a pathogen of maize, orthologs of Hm1 and the HC-toxin reductase activity are present in the grass family, suggesting an ancient and evolutionarily conserved role of this DR trait in plants. Here, we provide proof for such a role by demonstrating its involvement in nonhost resistance of barley to CCR1. Barley leaves in which expression of the Hm1 homologue was silenced became susceptible to infection by CCR1, but only if the pathogen was able to produce HC toxin. Phylogenetic analysis indicated that Hm1 evolved exclusively and early in the grass lineage. Given the devastating ability of CCR1 to kill maize, these findings imply that the evolution and/or geographical distribution of grasses may have been constrained if Hm1 did not emerge.