The 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.
