Minichromosome stability induced by partial genome duplication in Arabidopsis thaliana

A functional centromere lacking CentO sequences in a newly formed ring chromosome in rice

An awned rice (Oryza sativa) plant carrying a tiny extra chromosome was discovered among the progeny of a telotrisomic line 2n+4L. Fluorescence in situ hybridization (FISH) using chromosome specific BAC clones revealed that this extra chromosome was a ring chromosome derived from part of the long arm of chromosome 4. So the aneuploidy plant was accordingly named as 2n+4L ring. We did not detect any CentO FISH signals on the ring chromosome, and found only the centromeric probe Centromeric Retrotransposon of Rice (CRR) was co-localized with the centromere-specific histone CENH3 as revealed by sequential FISH after immunodetection. The extra ring chromosome exhibited a unique segregation pattern during meiosis, including no pairing between the ring chromosome and normal chromosome 4 during prophase I and pre-separation of sister chromatids at anaphase I.

Artificial Chromosome Preparation in Arabidopsis

In Arabidopsis thaliana, various attempts have been made to create artificial chromosomes as a new tool for cytological and genetic analyses. However, most of the efforts have been unsuccessful until recently. Most eukaryotic chromosomes are linear, and therefore the Arabidopsis artificial chromosomes have also been designed to be linear and to carry the telomere structure at both ends. In contrast, circular artificial chromosomes were successfully created by the Cre/LoxP system combined with Ac/Ds transposon system, on the basis of the discovery that ring minichromosomes are relatively stable and transmissible to the next generations in A. thaliana. Because ring minichromosomes ∼1 to 6 Mb in size have been generated, in this article, the protocol for inducing large chromosomal rearrangements resulting in ring chromosome formation is described. © 2016 by John Wiley & Sons, Inc.