Mechanisms linking bacterial chemotaxis signaling to nitrogen fixation in beneficial plant-associated bacteria

将细菌趋化信号与有益植物相关细菌固氮联系起来的机制

• 批准号: 2130556
• 负责人: Gladys Alexandre
• 金额: $ 95万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2130556&HistoricalAwards=false
• 关键词: Mechanisms; linking; bacterial; chemotaxis; signaling

Bacterial inoculants can enhance crop yields and reduce reliance on expensive and environmentally harmful chemical fertilizers which are needed to meet the demand for food of the expected global population of 9.7 billion by 2050. To be useful in the field, bacterial inoculants must not only express plant growth beneficial traits but must also be able to colonize plant roots. Further, many bacteria selected in the laboratory as bio-inoculants fail to consistently produce plant growth enhancements once applied in greenhouses or in the fields . This highlights shortcomings in our understanding of the behavior and physiology of beneficial bacteria in the rhizosphere. This project aims to elucidate the molecular mechanisms by which bio-inoculant bacteria coordinate expression of plant growth beneficial traits (nitrogen fixation) with functions that are critical for competitiveness in the rhizosphere and colonization of plant roots (chemotaxis). The knowledge gained from this research will contribute toward better predictive models to guide strategies to select and/or design beneficial diazotrophs for bio-inoculation applications, to improve crop management with benefits to society. In addition to addressing challenges related to sustainable agriculture through basic research, the project will engage a diverse community of participants in developing future solutions to these challenges. The project will provide research opportunities for high school and undergraduate students, including members from underrepresented groups, with those students included as co-authors in publications, when appropriate. The principal investigator will also continue engagement of deaf-and-hard-of-hearing undergraduate students in research experiences. The project will also provide graduate students and a postdoctoral fellow with opportunities to mentor undergraduate students and to apply their research communication skills in a breadth of outreach activities.Preliminary data suggest that bacterial chemotaxis signaling proteins regulate the expression of nitrogen fixation in the beneficial plant-colonizing and bio-inoculant diazotroph, Azospirillum brasilense. The investigators aim to determine the molecular mechanisms by which bacterial chemotaxis signaling proteins coordinate the induction of nitrogen fixation in diazotroph soil bacteria used as biofertilizers worldwide, and the role of this coupling in the rhizosphere, using genetics, live cell fluorescence microscopy and biochemical approaches. They will also explore the mechanism of an apparent similar coupling between metabolism and chemotaxis signaling in the pea symbiont, Rhizobium leguminosarum bv. viciae. Objective 1 will establish the mechanism(s) of chemotaxis signaling control of nitrogen metabolism in A. brasilense and specifically test the hypothesis that chemotaxis signaling proteins interact with an energy-responsive protein(s) to affect the expression of a transcriptional regulator of nitrogen fixation, RpoN. The spatio-temporal pattern of nitrogen fixation expression in the wheat rhizosphere and how chemotaxis affects this activity will also be determined. Objective 2 will decipher how a subset of chemoreceptors adjust chemotaxis signaling to support A. brasilense nitrogen fixation in the wheat rhizosphere. The role of oxygen- and energy-sensing chemoreceptors in affecting chemotaxis sensory specificity, nitrogen fixation and root colonization will be characterized. In addition, the role of one of these chemoreceptors in maintaining chemotaxis signaling arrays structural integrity will be elucidated. Objective 3 will explore how chemotaxis signaling array composition, which is affected by nutrient starvation, regulates nitrogen-fixing nodulation in R. leguminosarum. Together, the results obtained will provide insight into how distinct molecular functions (chemotaxis and nitrogen metabolism) evolved to become integrated within cells. These findings will also produce strategies to improve the performance of diazotroph bioinoculants by elucidating general design principles for the control of traits that contribute to rhizosphere plant-growth promoting competence. The research will employ genetically tractable model systems relevant to modern agriculture to address pressing environmental issues and sustainable agricultural practices. The results of this research will contribute toward better predictive models to guide strategies to select and/or design beneficial diazotrophs for bio-inoculation applications. This award is being co-funded by the Cellular Dynamics and Function cluster in the Division of Molecular and Cellular Biosciences, along with the Plant Biotic Interactions program in the Division of Integrative Organismal Systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

细菌接种剂可以提高作物产量，减少对昂贵且对环境有害的化学肥料的依赖，而这些化学肥料是到2050年满足预计97亿全球人口的粮食需求所必需的。为了在该领域中有用，细菌接种剂必须不仅表达植物生长有益性状，而且还必须能够定殖植物根部。 此外，在实验室中选择作为生物接种剂的许多细菌一旦应用于温室或田间就不能持续地产生植物生长增强。这突出了我们对根际有益细菌的行为和生理学理解的不足。该项目旨在阐明生物接种细菌协调植物生长有益性状（固氮）表达的分子机制，这些功能对根际竞争力和植物根的定殖（趋化性）至关重要。 从这项研究中获得的知识将有助于更好的预测模型，以指导选择和/或设计有益的固氮生物用于生物接种应用的策略，以改善作物管理，造福社会。除了通过基础研究应对与可持续农业有关的挑战外，该项目还将让各种参与者参与制定未来应对这些挑战的解决方案。 该项目将为高中生和本科生提供研究机会，包括代表性不足的群体的成员，并酌情将这些学生列为出版物的共同作者。主要研究者还将继续参与听力障碍和听力障碍的本科生的研究经验。该项目还将为研究生和博士后提供指导本科生的机会，并将他们的研究交流技能应用于广泛的推广活动。初步数据表明，细菌趋化性信号蛋白调节固氮在有益的植物定殖和生物接种剂固氮菌，Azoacetyllum brasilense的表达。 研究人员的目的是确定细菌趋化性信号蛋白协调固氮土壤细菌作为生物肥料在世界各地的诱导固氮的分子机制，以及这种耦合在根际的作用，使用遗传学，活细胞荧光显微镜和生物化学方法。他们还将探讨豌豆共生体根瘤菌（Rhizobium leguminosarum bv.）中代谢和趋化性信号之间明显相似的耦合机制。蚕豆目的1探讨趋化性信号调控A. brasilense，并具体测试了趋化性信号蛋白与能量响应蛋白相互作用以影响固氮转录调节因子RpoN的表达的假设。还将确定小麦根际固氮表达的时空模式以及趋化性如何影响这种活动。目的2将阐明化学感受器的一个子集如何调节趋化性信号以支持A.小麦根际固氮作用的研究氧和能量感应化学感受器的作用，影响趋化性的感觉特异性，固氮和根殖民的特点。此外，这些化学感受器在维持趋化性信号阵列结构完整性的作用将得到阐明。目的3探讨趋化性信号阵列的组成如何受营养饥饿的影响而调控固氮作用。豆科植物总之，所获得的结果将提供洞察不同的分子功能（趋化性和氮代谢）如何演变成为细胞内的整合。这些研究结果也将产生战略，以改善固氮生物接种剂的性能，阐明一般设计原则，有助于根际植物生长促进能力的性状控制。该研究将采用与现代农业相关的遗传学上易于处理的模型系统，以解决紧迫的环境问题和可持续的农业实践。这项研究的结果将有助于更好的预测模型，以指导战略选择和/或设计有益的固氮生物接种应用。该奖项由分子和细胞生物科学部的细胞动力学和功能组沿着综合有机体系统部的植物生物相互作用项目共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Azospirillum brasilense AerC and Tlp4b Cytoplasmic Chemoreceptors Are Promiscuous and Interact with the Two Membrane-Bound Chemotaxis Signaling Clusters Mediating Chemotaxis Responses

• DOI: 10.1128/jb.00484-22
• 发表时间: 2023-05
• 期刊: Journal of Bacteriology
• 影响因子: 3.2
• 作者: E. Ganusova;Madison Rost;A. Aksenova;Mustafa Abdulhussein;Alisha Holden;G. Alexandre