Abstract：
Xylem-limited bacterial pathogens cause some of the most destructive plant diseases. Though imposed measures to control these pathogens are generally ineffective, even among susceptible taxa, some hosts can limit bacterial loads and symptom expression. Mechanisms by which this resistance is achieved are poorly understood. In particular, it is still unknown how differences in vascular structure may influence biofilm growth and spread within a host. To address this, we developed a novel theoretical framework to describe biofilm behaviour within xylem vessels, adopting a polymer-based modelling approach. We then parameterised the model to investigate the relevance of xylem vessel diameters on Xylella fastidiosa resistance among olive cultivars. The functionality of all vessels was severely reduced under infection, with hydraulic flow reductions of 2-3 orders of magnitude. However, results suggest wider vessels act as biofilm incubators; allowing biofilms to develop over a long time while still transporting them through the vasculature. By contrast, thinner vessels become blocked much earlier, limiting biofilm spread. Using experimental data on vessel diameter distributions, we were able to determine that a mechanism of resistance in the olive cultivar Leccino is a relatively low abundance of the widest vessels, limiting X. fastidiosa spread.
摘要：
木质部有限的细菌病原体引起一些最具破坏性的植物病害。尽管控制这些病原体的措施通常是无效的，即使在易感类群中，一些宿主可以限制细菌负荷和症状表达。实现这种抗性的机制知之甚少。特别是,目前尚不清楚血管结构的差异如何影响生物膜在宿主内的生长和扩散。为了解决这个问题，我们开发了一个新的理论框架来描述木质部血管内的生物膜行为，采用基于聚合物的建模方法。然后，我们对模型进行了参数化，以研究木质部血管直径与橄榄品种中木质部抗性的相关性。感染下所有血管的功能严重下降，液压流量减少2-3个数量级。然而,结果表明，更宽的血管充当生物膜孵化器;允许生物膜长时间发展，同时仍然通过脉管系统运输。相比之下,较薄的血管更早被阻塞，限制生物膜传播。使用血管直径分布的实验数据，我们能够确定橄榄品种Leccino的抗性机制是最宽血管的丰度相对较低，限制X.fastidiosa传播。
