The supernumerary B chromosome of maize: drive and genomic conflict

J. A. Birchler and H. Yang,  Open Biol,  11:210197. 2021.

The supernumerary B chromosome of maize is dispensable, containing no vital genes, and thus is variable in number and presence in lines of maize. In order to be maintained in populations, it has a drive mechanism consisting of nondisjunction at the pollen mitosis that produces the two sperm cells, and then the sperm with the two B chromosomes has a preference for fertilizing the egg as opposed to the central cell in the process of double fertilization. The sequence of the B chromosome coupled with B chromosomal aberrations has localized features involved with nondisjunction and preferential fertilization, which are present at the centromeric region. The predicted genes from the sequence have paralogues dispersed across all A chromosomes and have widely different divergence times suggesting that they have transposed to the B chromosome over evolutionary time followed by degradation or have been co-opted for the selfish functions of the supernumerary chromosome.

More related to this:

Evolution and biology of supernumerary B chromosomes

The maize Ab 10 meiotic drive system maps to supernumerary sequences in a large complex haplotype

Researchers report reference genome for maize B chromosome

B Chromosomes and Sex in Animals

B Chromosomes – A matter of chromosome drive

B chromosomes in plants: escapees from the A chromosome genome?