title: Nondisjunction in favor of a chromosome: the mechanism of rye B chromosome drive during pollen mitosis.
abstract: B chromosomes (Bs) are supernumerary components of the genome and do not confer any advantages on the organisms that harbor them. The maintenance of Bs in natural populations is possible by their transmission at higher than Mendelian frequencies. Although drive is the key for understanding B chromosomes, the mechanism is largely unknown. We provide direct insights into the cellular mechanism of B chromosome drive in the male gametophyte of rye (Secale cereale). We found that nondisjunction of Bs is accompanied by centromere activity and is likely caused by extended cohesion of the B sister chromatids. The B centromere originated from an A centromere, which accumulated B-specific repeats and rearrangements. Because of unequal spindle formation at the first pollen mitosis, nondisjoined B chromatids preferentially become located toward the generative pole. The failure to resolve pericentromeric cohesion is under the control of the B-specific nondisjunction control region. Hence, a combination of nondisjunction and unequal spindle formation at first pollen mitosis results in the accumulation of Bs in the generative nucleus and therefore ensures their transmission at a higher than expected rate to the next generation.
authors.affiliation: Leibniz Institute of Plant Genetics and Crop Plant Research, 06466 Gatersleben, Germany.
authors.forename: Ali M
authors.initials: AM
authors.lastname: Banaei-Moghaddam
authors.forename: Veit
authors.initials: V
authors.lastname: Schubert
authors.forename: Katrin
authors.initials: K
authors.lastname: Kumke
authors.forename: Oda
authors.initials: O
authors.lastname: Weiβ
authors.forename: Sonja
authors.initials: S
authors.lastname: Klemme
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Nagaki
authors.forename: Jirí
authors.initials: J
authors.lastname: Macas
authors.forename: Mónica
authors.initials: M
authors.lastname: González-Sánchez
authors.forename: Victoria
authors.initials: V
authors.lastname: Heredia
authors.forename: Diana
authors.initials: D
authors.lastname: Gómez-Revilla
authors.forename: Miriam
authors.initials: M
authors.lastname: González-García
authors.forename: Juan M
authors.initials: JM
authors.lastname: Vega
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Puertas
authors.forename: Andreas
authors.initials: A
authors.lastname: Houben
mesh_terms: D002503:Centromere / Q000378:metabolism; D032461:Chromosomes, Plant / Q000502:physiology* / Q000648:ultrastructure; D015321:Gene Rearrangement; D006657:Histones / Q000378:metabolism; D008938:Mitosis; D008969:Molecular Sequence Data; D009630:Nondisjunction, Genetic; D011058:Pollen / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D012434:Secale / Q000235:genetics* / Q000648:ultrastructure
chemical_list: D006657:Histones