Sequence of the supernumerary B chromosome of maize provides insight into its drive mechanism and evolution

Nicolas Blavet, Hua Yang, Handong Su, Pavel Solanský, Ryan N. Douglas, Miroslava Karafiátová, Lucie Šimková, Jing Zhang, Yalin Liu, Jie Hou, Xiaowen Shi, Chen Chen, Mohamed El-Walid, Morgan E. McCaw, Patrice S. Albert, Zhi Gao, Changzeng Zhao, Gil Ben-Zvi, Lior Glick, Guy KolJinghua Shi, Jan Vrána, Hana Šimková, Jonathan C. Lamb, Kathleen Newton, R. Kelly Dawe, Jaroslav Doležel, Tieming Ji, Kobi Baruch, Jianlin Cheng, Fangpu Han, James A. Birchler, Jan Bartoš

Research output: Contribution to journalArticlepeer-review


B chromosomes are enigmatic elements in thousands of plant and animal genomes that persist in populations despite being nonessential. They circumvent the laws of Mendelian inheritance but the molecular mechanisms underlying this behavior remain unknown. Here we present the sequence, annotation, and analysis of the maize B chromosome providing insight into its drive mechanism. The sequence assembly reveals detailed locations of the elements involved with the cis and trans functions of its drive mechanism, consisting of nondisjunction at the second pollen mitosis and preferential fertilization of the egg by the B-containing sperm. We identified 758 protein-coding genes in 125.9 Mb of B chromosome sequence, of which at least 88 are expressed. Our results demonstrate that transposable elements in the B chromosome are shared with the standard A chromosome set but multiple lines of evidence fail to detect a syntenic genic region in the A chromosomes, suggesting a distant origin. The current gene content is a result of continuous transfer from the A chromosomal complement over an extended evolutionary time with subsequent degradation but with selection for maintenance of this nonvital chromosome.

Original languageEnglish
Article numbere2104254118
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number23
StatePublished - 29 Apr 2021
Externally publishedYes


  • B chromosome
  • Genetic drive
  • Nondisjunction
  • Preferential fertilization


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