Engineered Minichromosomes in Plants: Structure, Function, and Applications

Abstract

Engineered minichromosomes are small chromosomes that contain a transgene and selectable marker, as well as all of the necessary components required for maintenance in an organism separately from the standard chromosome set. The separation from endogenous chromosomes makes engineered minichromosomes useful in the production of transgenic plants. Introducing transgenes to minichromosomes does not have the risk of insertion within a native gene; additionally, transgenes on minichromosomes can be transferred between lines without the movement of linked genes. Of the two methods proposed for creating engineered minichromosomes, telomere-mediated truncation is more reliable in plant systems. Additionally, many plants contain a supernumerary, or B chromosome, which is an excellent starting material for minichromosome creation. The use of site-specific recombination systems in minichromosomes can increase their utility, allowing for the addition or subtraction of transgenes in vivo. The creation of minichromosomes with binary bacterial artificial chromosome vectors provides the ability to introduce many transgenes at one time. Furthermore, coupling minichromosomes with haploid induction systems can facilitate transfer between lines. Minichromosomes can be introduced to a haploid-inducing line and crossed to target lines. Haploids of the target line that then contain a minichromosome can then be doubled. These homozygous lines will contain the transgene without the need for repeated introgressions.

Keywords: B chromosome; Gene stacking; Genome editing; Minichromosome; Plant transformation; Site-specific recombination; Synthetic chromosome; Telomere truncation.