Molecular mechanisms of dormancy and germination in parasitic and non-parasitic plants

非洲粮食安全的主要障碍之一是由一种名为striga hermonthica的寄生植物造成的侵扰。稻瘟病菌寄生在高粱、水稻和谷子等主要粮食作物上，使1亿多自给农民损失30%至100%的产量。作为一种专性的半寄生植物，它不能独立生存，只能依靠侵染寄主来获得营养、水分和同化物。只有当潜在的寄主在附近时，Striga种子才能“苏醒”(萌发)并开始生长，这是至关重要的。因此，Striga进化出了与非寄生植物截然不同的独特策略。例如，种子通常会对光线和赤霉酸(GA)等植物激素做出反应而萌发。然而，Striga不会对这些信号做出反应。相反，Striga种子在检测到一种名为strigolactone(SL)的植物激素时就会苏醒。这种化学信号由植物宿主释放到土壤中，以促进与真菌的有益相互作用。Striga对寄主来源的SLS的依赖是一个弱点，可用于开发抗击Striga侵扰的技术。这将需要对Striga种子如何将SL作为土壤中的“唤醒”信号进行详细的机械理解。不足为奇的是，有许多信号会影响种子发芽的决定。种子必须整合所有这些信息，并将其转化为基因表达。基因表达的某些组合组成了一个“发芽密码”，指示种子是否醒来。在许多方面，Striga重新连接了这种萌发代码，因为它依赖SLS，而不是环境线索来触发萌发。Lumba实验室将结合转录学和大规模蛋白质相互作用研究等尖端方法，确定Striga如何重新连接代码。在我的博士后期间，我成功地应用这些方法构建了拟南芥中的蛋白质相互作用网络。我们的方法将确定对Striga发芽重要的成分，并基于高通量酵母双杂交方法检查这些成分是如何相互作用的。我的团队将应用系统生物学方法来建立信号网络，这将揭示各种信号如何汇聚形成萌发代码。为了了解代码的进化，我们将构建Striga和拟南芥组件的网络。比较这些网络将揭示Striga获得或丢失的蛋白质相互作用，这将为Striga寄生生活方式的进化提供洞察。意义：尽管Striga对1亿人造成毁灭性影响，但寄生植物萌发的分子机制在很大程度上是未知的。阐明这些机制，不仅将回答生物学中的基本进化问题，而且还将导致解决斯特里加的祸害。

One of the major impediments to food security in Africa is infestation caused by a parasitic plant called Striga hermonthica. Striga parasitizes major food crops like sorghum, rice and millet, which results in 30 to 100% yield losses for over 100 million subsistence farmers. As an obligate hemiparasitic plant, Striga cannot survive on its own and relies on infecting a plant host in order to obtain nutrients, water and assimilates. It is essential that Striga seed “wake up” (germinate) and begin growing only when a potential host is nearby. As a result, Striga has evolved unique strategies that are distinct from non-parasitic plants. For example, seeds typically germinate in response to light and plant hormones like gibberellic acid (GA). Striga, however, does not respond to these signals. Instead, Striga seeds wake up upon detecting a class of plant hormones called strigolactones (SL). This chemical signal is released into the soil by plant hosts to promote a beneficial interaction with fungi. Striga's dependence on host-derived SLs is a weakness that can be exploited for the development of technologies to combat Striga infestations. This will require a detailed mechanistic understanding of how Striga seeds use SL as a “wake up” signal in the soil. Not surprisingly, there are many signals that affect the seed's decision to germinate. Seeds have to integrate all of this information and translate it into gene expression. Certain combinations of gene expression make up a “germination code” to instruct a seed whether or not to wake up. In many ways, Striga has rewired this germination code because of its dependence on SLs, rather than environmental cues, to trigger germination. The Lumba Lab will determine how Striga has rewired the code by combining cutting-edge approaches such as transcriptomics and large-scale protein interaction studies. During my post-doc, I successfully applied these methods to construct protein interaction networks in Arabidopsis thaliana. Our approach will identify components that are important for germination in Striga and examine how these components interact based on high-throughput yeast two-hybrid methods. My group will apply systems biology approaches to build signalling networks which will reveal how various signals converge to form the germination code. To understand the evolution of the code, we will construct networks of Striga and Arabidopsis components. Comparing these networks will reveal protein interactions that have been gained or lost by Striga, which will provide insight about the evolution of Striga's parasitic lifestyle.Significance: Despite the devastating effects of Striga on 100 million people, molecular mechanisms underlying germination in parasitic plants are largely unknown. Elucidating these mechanisms, not only will answer fundamental evolutionary questions in biology but also lead to solutions in combating the scourge of Striga.