Chemotaxis sensing preference in plant-microbe associations

未来的粮食安全将取决于采用可持续农业做法提高作物产量，以满足预计到2050年将达到97亿的世界人口的粮食需求。植物根际的微生物组（根周围的区域被称为根际，一个区域中的微生物组被称为微生物组），可以与其人类肠道同源物进行比较，在植物健康中起着关键作用，最终影响作物产量。操纵根际微生物是实现可持续农业实践的一项拟议战略。然而，关于大多数有益的土壤细菌如何找到它们的目标植物，以及一旦它们找到植物，它们如何与植物的根部建立稳定的联系，人们知之甚少。这一知识缺口将通过研究细菌如何在其表面部署化学检测蛋白以及研究来自这些传感蛋白的信号如何进入细胞内部并在细胞内移动来解决。这项工作将提供有关有益土壤细菌如何在根表面精确找到其首选区域的详细定量信息，结果将为优化有益植物-细菌协会的设计提供新的工具。该项目将通过为来自不同背景的本科生和研究生提供研究培训来产生教育影响，包括来自STEM代表性不足的群体的学生。该项目还将使聋人和重听学生参与研究，从而加强这一严重缺乏服务和尚未开发的人才库的参与。该项目将利用活动土壤细菌Azoacellum brasilense的良好特征的趋化反应作为模型，因为它是根部栖息细菌的合适代表，并且在可持续农业实践中成功地用于促进各种作物的生长。实验设计结合了蛋白质组学，遗传学和计算建模，以解决能动细菌如何设置根的传感偏好。首先，将建立不同的趋化性受体阵列，这是典型的许多有益的根定殖细菌的组装的机制（目标1）。接下来，趋化性受体簇组成的动态变化将与根际细菌的感知偏好和竞争性的变化相关（目标2）。由于趋化性来自复杂的信号通路，因此很难从分子机制预测种群行为。实验数据将与计算建模相结合，以定量描述运动细菌如何随着其代谢的变化而设置趋化性传感偏好，以精确地在梯度中的特定位置处积累（目标3）。所获得的结果将揭示工程原理的操纵和/或合成设计的趋化性感测偏好有益的土壤细菌。这些知识对于制定未来的可持续农业根际微生物组优化战略至关重要。

Future food security will rely on increased crop yields using sustainable agricultural practices to meet the demands for food of the projected world population of 9.7 billion by 2050. The microbiome of the plant rhizosphere (the area around the root is known as the rhizosphere, and the group of microbes in an area is known as a microbiome), which can be compared to its human gut homolog, plays a critical role in plant health, ultimately affecting crop yield. Manipulation of the rhizosphere microbes is a proposed strategy for the achievement of sustainable agricultural practices. However, little is known regarding how most beneficial soil bacteria manage to find their target plants, and how they establish stable associations with the roots of plants once they find them. This gap in knowledge will be addressed by examining how bacteria deploy chemical detecting proteins on their surfaces and by studying how the signals from those sensing proteins enter and move around inside the cell. The work will provide detailed quantitative information about how beneficial soil bacteria precisely find their preferred zones on the root surface, and the results will provide new tools for optimizing design of beneficial plant-bacteria associations. The project will have educational impact by providing research training for undergraduate and graduate students from diverse backgrounds, including those from underrepresented groups in STEM. The project will also engage deaf and hard of hearing students in research and thus enhance participation of this critically underserved and untapped pool of talent. This project will take advantage of the well-characterized chemotaxis response of the motile soil bacterium, Azospirillum brasilense, as a model because it is a suitable representative of root inhabiting bacteria and it is successfully used to promote the growth of diverse crops in sustainable agricultural practices. The experimental design combines proteomics, genetics and computational modeling to address how motile bacteria set sensing preferences for roots. First, the mechanisms underlying the assembly of distinct chemotaxis receptor arrays which are typical of many beneficial root colonizing bacteria will be established (Objective 1). Next, the dynamic changes in the composition of chemotaxis receptor clusters will be related with changes in bacteria sensing preference and competitiveness in the rhizosphere (Objective 2). Because chemotaxis emerges from a sophisticated signaling pathway, it is difficult to predict population behavior from molecular mechanisms. The experimental data will be integrated with computational modeling to quantitatively describe how motile bacteria set chemotaxis sensing preference with change in their metabolism to precisely accumulate at a specific position in a gradient (Objective 3). Results obtained will uncover the engineering principles for manipulation of and/or the synthetic design of chemotaxis sensing preferences in beneficial soil bacteria. This knowledge is critical to develop future strategies for rhizosphere microbiome optimization for sustainable agriculture.