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. Copyright (C) 2016, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Limited and Science Press. All rights reserved.