Telomere truncation has been shown to be an efficient technology for the creation of minichromosomes, which can be used as artificial chromosome platforms for genetic engineering. Artificial chromosome based genetic engineering is considered to be superior to existing techniques of randomized gene integration by Agrobacterium or biolistic mediated genetic transformation. It organizes multiple transgenes as a unique genetic linkage block for subsequently manipulations in breeding. Telomere truncation technology relies on three components: the telomere sequence that mediates chromosomal truncation, a selection marker that allows the selection of transgenic events, and a site specific recombination system that can be used to accept future genes into the minichromosome by gene targeting. These elements are usually pre-assembled before transformation which is time and labor consuming. We found in this research that the three elements could be mixed to transform plant cells in a biolistic transformation, and produced efficient chromosomal truncations and minichromosomes in rice. This system will allow rapid constructions of minichromosomes with a flexible selection of resistant markers, site specific recombination systems and other desirable elements. In addition, a rice telotrisomic line was used as the starting material for chromosomal truncations. Minichromosomes from the truncations of both the telocentric chromosome and other chromosomes were recovered. The minichromosomes remained stable during two years of subculture. The construction of minichromosomes in rice, an economically important crop, will provide a platform for future artificial chromosome based genetic engineering of rice for the stacking of multiple genes.

Keywords:minichromosome;telomere truncation;artificial chromosome;telotrisomic;Oryza sativa;technical advance