| Abstract | A system for engineering plant chromosomes has been developed to facilitate the introduction of novel genes into the plant genome. The system is based on the establishment of a unique genetic locus within the ribosomal DNA (rDNA) region of the host chromosome to provide a permissive environment for expression of the introduced genes of interest (GOI). The genetic locus can exist within an independent, fully functional "minichromosome" (MC) or as a segment of a modified host chromosome (termed Engineered Trait Locus or ETL). The site-specific integration of transgenes to the rDNA locus isolates them from other endogenous genes, an advantage over conventional transformation in which foreign genes are inserted randomly into the host genome. Furthermore, MCs or ETLs can confer stability and high expression of the transgenes, as demonstrated in mammalian systems. To evaluate this system in plants, several MC and ETL lines have been generated in soybean, an important crop used worldwide for protein and oil consumption. The characterization of a soybean line containing an MC demonstrates that 1) the MC is stable over multiple generations as well as in field conditions, 2) maintaining the MC has no adverse phenotypic consequences, and 3) the MC can provide high-level expression of the introduced GOI. |
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