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

大米等谷物是人类和动物营养的主食。由于谷物的生长受到氮素的限制，这些作物的高产目前依赖于化肥，化肥是农场的一项主要支出，并造成重大的环境破坏。鉴于对这些作物增产的需求日益增加，制定替代战略以提高作物产量，同时减少化肥使用量是当务之急。一种这样的策略是利用根瘤菌，这种根瘤菌与这些作物形成密切的内生联系，促进它们的生长。根瘤菌是一种土壤细菌，能与豆类形成非常有效的固氮作用。最近的研究表明，根瘤菌劫持了与菌根真菌共生的豆科植物的遗传机制。与豆类相似，水稻与菌根真菌形成共生关系，并包含与根瘤菌相互作用所需的豆类基因的同源基因。研究人员实验室的初步结果表明，一株根瘤菌利用菌根共生途径来定植水稻组织。该项目的目标是确定导致这种有益联系的根瘤菌和水稻的分子和细胞机制，并评估根瘤菌与水稻固氮的潜力。这种根瘤菌-谷物的相互作用提供了一个独特的机会来研究可能允许豆类结瘤出现的最初关系和互惠互利，而且从长远来看，通过遵循豆类进化的道路，使用这个系统来设计谷物的固氮工程。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的跨学科培训，包括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、研究生和博士后提供大量的外展和教育机会。微生物共生的好处也将在两个实验室针对少数族裔本科生和K-12学生的定向研究计划中得到强调，并利用威斯康星大学两个校区的公共推广计划。

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.