Collaborative Research: understanding and utilizing a unique association between rhizobia and rice

谷物如水稻（Oryza sativa）是人类和动物营养的主食。由于谷物生长受到氮的限制，这些作物的高产目前依赖于化肥，这是一项主要的农场开支，并造成重大的环境破坏。鉴于对提高这些作物产量的需求日益增加，制定替代战略以提高作物产量，同时减少化肥使用量是高度优先事项。其中一种策略是使用与这些作物形成密切内生联系并促进其生长的根瘤菌。根瘤菌是土壤细菌，与豆类植物形成非常有效的固氮联合体。最近的研究表明，根瘤菌劫持了豆科植物与菌根真菌共生的遗传机制。与豆科植物相似，水稻与菌根真菌形成共生关系，并含有与根瘤菌相互作用所必需的豆科植物基因的同源物。来自研究者实验室的初步结果表明，根瘤菌菌株利用菌根共生途径来定殖水稻组织。本项目的目标是确定根瘤菌和水稻的分子和细胞机制，导致这种有益的协会，以及评估根瘤菌固氮与水稻的潜力。这种根瘤菌-谷物的相互作用提供了一个独特的机会，可以研究最初的关系和互利，这可能使豆科植物的繁殖出现，但从长远来看，利用这一系统，通过遵循豆科植物进化的路径来设计谷物中的固氮作用。该项目对教育和专业发展的更广泛影响包括对学生和博士后研究员的跨学科培训，包括在微生物和植物遗传学、分子生物学、显微镜和植物-微生物相互作用方面的经验。将为本科生、研究生和博士后学生提供许多外联和教育机会。微生物共生的好处也将在针对少数民族本科生和K-12学生在两个实验室的定向研究计划，以及使用在威斯康星州的两个校区的公共推广计划强调。

Cereals such as rice (Oryza sativa) are staple food for human and animal nutrition. Because cereal growth is limited by nitrogen, the high yields of these crops are currently dependent on fertilizers that are a major on-farm expense and cause significant environmental damages. In view of the increasing demand for higher production of these crops, the development of alternative strategies to enhance crop production while reducing fertilizer use is of high priority. One such strategy is to use rhizobia that form intimate endophytic association with these crops and increase their growth. Rhizobia are soil bacteria that form a very efficient nitrogen-fixing association with legumes. Recent studies have shown that rhizobia hijacked the genetic machinery of legumes involved in symbiosis with mycorrhizal fungi. Similar to legumes, rice forms symbiosis with mycorrhizal fungi and contain the homologues of legume genes necessary for interactions with rhizobia. Preliminary results from the investigators' laboratories indicate that a rhizobial strain utilizes the mycorrhizal symbiotic pathway to colonize rice tissues. The goal of this project is to determine the molecular and cellular mechanisms of both rhizobia and rice that result in this beneficial association as well as to evaluate the potential of rhizobial nitrogen fixation with rice. This rhizobial-cereal interaction provides a unique opportunity to study the initial relationships and mutual benefits that probably allowed legume nodulation to appear but also, in the long term, to use this system to engineer nitrogen fixation in cereals by following the path of legume evolution.The broader impacts of this project for the education and professional development include the interdisciplinary training for students and postdoctoral fellow that include experience in microbial and plant genetics, molecular biology, microscopy and plant-microbe interactions. Numerous outreach and educational opportunities will be provided for undergraduate, graduate and postdoctoral students. The benefits of microbial symbioses will also be emphasized in directed research programs targeting minority undergraduate and K-12 students in both laboratories as well as using the public outreach programs in both campuses of the University of Wisconsin.