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 McCaw, Patrice S. Albert, Zhi Gao, Changzeng Zhao, Gil Ben-Zvi, Lior Glick, Guy Kol, Jinghua Shi, Jan Vrána, Hana Šimková, Jonathan C. Lamb, Kathleen J. Newton, R. Kelly Dawe, Jaroslav Doležel, Tieming Ji, Kobi Baruch, Jianlin Cheng, Fangpu Han, James A. Birchler, Jan Bartoš
Abstract
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.