Abstract：
The modification of seed shattering has been a recurring theme in rice evolution. The wild ancestor of cultivated rice disperses its seeds, but reduced shattering was selected during multiple domestication events to facilitate harvesting. Conversely, selection for increased shattering occurred during the evolution of weedy rice, a weed invading cultivated rice fields that has originated multiple times from domesticated ancestors. Shattering requires formation of a tissue known as the abscission zone (AZ), but how the AZ has been modified throughout rice evolution is unclear. We quantitatively characterized the AZ characteristics of relative length, discontinuity, and intensity in 86 cultivated and weedy rice accessions. We reconstructed AZ evolutionary trajectories and determined the degree of convergence among different cultivated varieties and among independent weedy rice populations. AZ relative length emerged as the best feature to distinguish high and low shattering rice. Cultivated varieties differed in average AZ morphology, revealing lack of convergence in how shattering reduction was achieved during domestication. In contrast, weedy rice populations typically converged on complete AZs, irrespective of origin. By examining AZ population-level morphology, our study reveals its evolutionary plasticity, and suggests that the genetic potential to modify the ecologically and agronomically important trait of shattering is plentiful in rice lineages.
摘要：
种子破碎的修饰一直是水稻进化中反复出现的主题。栽培水稻的野生祖先分散了种子，但是在多个驯化事件中选择了减少的粉碎以促进收获。相反，在杂草稻的进化过程中发生了增加破碎的选择，一种入侵栽培稻田的杂草，多次起源于驯化的祖先。粉碎需要形成称为脱落区（AZ）的组织，但是在整个水稻进化过程中，AZ是如何被修改的还不清楚。我们定量表征了相对长度的AZ特征，不连续性,86种栽培稻和杂草稻的强度。我们重建了AZ的进化轨迹，并确定了不同栽培品种之间以及独立杂草稻种群之间的趋同程度。AZ相对长度是区分高，低碎米的最佳特征。栽培品种的平均AZ形态不同，揭示了在驯化过程中如何实现破碎的减少缺乏收敛性。相比之下,杂草水稻种群通常聚集在完整的AZs上，不管起源。通过检查AZ人口水平的形态学，我们的研究揭示了它的进化可塑性，并表明在水稻谱系中修饰生态和农学上重要的破碎性状的遗传潜力是丰富的。
