Producing mimosine-free Leucaena leucocephala through metabolic pathway engineering

CBET-0827057 Borthakur主要研究者（PI）试图通过代谢途径工程开发一种不含含羞草碱的银合欢，这种银合欢可用作饲料，对动物没有任何有害的副作用。 银合欢是热带、亚热带国家重要的农林复合树种。银合欢被称为“热带的苜蓿”，因为它的叶子的高蛋白质含量与苜蓿相当。然而，银合欢植物含有一种毒素，含羞草碱，这是有害的动物。 由于含羞草素的生物合成途径尚不清楚，银合欢属植物不易转化，因此生产无含羞草素的银合欢是一项具有挑战性的任务。通过从银合欢共生菌中引入基因，将为银合欢中含羞草碱的去除提供一种新的代谢工程策略。该项目将使用两个根瘤菌基因，这是降解3-羟基-4-吡啶酮（HP）所必需的，这是银合欢中含羞草碱生物合成的前体。通过在转基因银合欢中表达这些基因，含羞草素的代谢途径将被重新定向，以产生氨，丙酮酸和甲酸，这应该作为额外的氮和碳源的植物。这项工作将引导其他豆类和非豆类植物中的毒素的中和代谢工程方法。夏威夷是全年测试生物工程作物的主要地点，需要许多科学家和训练有素的技术人员。该项目将通过培训两名生物技术研究生和六名或六名以上本科生，帮助在不久的将来培养一批科学家。将作出特别努力，通过这一项目招募夏威夷土著和其他太平洋岛屿学生接受培训。该项目还将通过培训24名科学教师来加强夏威夷的生物技术教育。教师将学习生物技术的最新发展，然后将其传递给学生。生物技术教育对于激发高中生对这一快速发展的技术的兴趣至关重要。如果没有适当的生物技术教育，公众就有可能接受对生物技术、转基因作物及其在夏威夷的试验的负面宣传。

CBET-0827057BorthakurThe Principal Investigators (PIs) seek to develop, through metabolic pathway engineering, a mimosine-free leucaena that can be used as a fodder without any harmful side effects to animals. Leucaena leucocephala (leucaena) is an important leguminous tree for agro-forestry in many tropical and subtropical countries. Leucaena is known as "the alfalfa of the tropics" since the high protein content of its foliage is comparable to that of alfalfa. However, leucaena plants contain a toxin, mimosine, which is harmful to animals. Producing mimosine-free leucaena is a challenging task because the biosynthetic pathway for mimosine is unknown and leucaena is recalcitrant to transformation. A novel metabolic engineering strategy will be used for removing mimosine from leucaena by introducing genes from its bacterial symbiont. This project will use two Rhizobium genes that are required for degradation of 3-hydroxy-4-pyridone (HP), which is a precursor for mimosine biosynthesis in leucaena. By expressing these genes in transgenic leucaena, the metabolic pathway for mimosine will be redirected to produce ammonia, pyruvate and formate, which should serve as additional nitrogen and carbon sources for the plant.This work will lead the way for neutralization of toxins in other legumes and non-legumes using metabolic engineering approaches. Hawaii is a prime location for testing bioengineered crops throughout the year, for which many scientists and trained technicians are needed. This project will help to create a group of scientists for the near future by training two graduate and six or more undergraduate students in biotechnology. Special efforts will be made to recruit the native Hawaiian and other Pacific Island students for training through this project. This project will also enhance biotechnology education in Hawaii by training 24 science teachers. Teachers will learn the latest developments in biotechnology, which will be then transmitted to the students. Biotechnology education is essential to stimulate interest of high school students to this rapidly growing technology. Without proper biotechnology education there is always a danger that the public may absorb negative publicity against biotechnology, transgenic crops, and their testing in Hawaii.