Non-random gene organization in eukaryotes plays a significant role in genome evolution. Here, we investigate the origin of a biosynthetic gene cluster for production of defence compounds in oat—the avenacin cluster. We elucidate the structure and organisation of this 12-gene cluster, characterise the last two missing pathway steps, and reconstitute the entire pathway in tobacco by transient expression. We show that the cluster has formed de novo since the divergence of oats in a subtelomeric region of the genome that lacks homology with other grasses, and that gene order is approximately colinear with the biosynthetic pathway. We speculate that the positioning of the late pathway genes furthest away from the telomere may mitigate against a ‘self-poisoning’ scenario in which toxic intermediates accumulate as a result of telomeric gene deletions. Our investigations reveal a striking example of adaptive evolution underpinned by remarkable genome plasticity.

真核生物中的非随机基因组织在基因组进化中发挥着重要作用。在这里，我们研究了燕麦中用于生产防御化合物的生物合成基因簇——燕麦素簇的起源。我们阐明了这个 12 基因簇的结构和组织，描述了最后两个缺失的途径步骤，并通过瞬时表达重建了烟草中的整个途径。我们表明，自从燕麦基因组亚端粒区域中与其他禾本科植物缺乏同源性的分歧以来，该簇就从头形成，并且该基因顺序与生物合成途径大致共线。我们推测，将晚期途径基因定位在距离端粒最远的位置可能会减轻“自我中毒”的情况，在这种情况下，由于端粒基因删除而导致有毒中间体积累。我们的研究揭示了一个以显着的基因组可塑性为基础的适应性进化的惊人例子。