“Centromere Drive: Cellular Mechanisms, Consequences and Significance in Meiosis and Creating Variability”

 

 Centromeres are chromosomal regions responsible for proper chromosome segregation in eukaryotes. Proper centromere function is essential for maintaining the ploidy level of organisms. Given this vital role, centromeric DNA and proteins are expected to evolve under strict evolutionary constraint. In contrast to this prediction, centromeric DNA and proteins evolve rapidly across diverse eukaryotic taxa. This evolutionary enigma is known as the centromere paradox. The centromere drive model provides a plausible explanation for this. The model posits that centromeric DNA evolves rapidly, which is often associated with fitness costs. To suppress this, centromeric proteins also evolve, thereby equalizing centromere strengths^1.

Some commonly found instances are segregation distortion in Drosophila melanogaster, Mimulus guttatus, Abnormal chromosome 10 (Ab 10) in maize, spore killers in ascomycetes, etc. In interspecific monkeyflower (Mimulus sps) hybrids, the D locus exhibits a 98:2 transmission advantage via female meiosis^2. Ab 10 chromosomes in maize containing heterochromatic knobs cheat female meiosis by forming neocentromeres that bias their segregation into the future egg cell^3. Segregation Distorter (SD) is an autosomal meiotic drive gene complex found worldwide in natural populations of Drosophila melanogaster. It leads to up to 99% of transmission advantage^4.

The centromere drive model predicts that the rapid divergence of centromeres could underlie reproductive isolation between species, leading to hybrid incompatibility and speciation. Diversity in centromeric proteins (CENH3) between species may lead to a range of aneuploids and haploids when they are crossed. Overall, centromere drive can have significant consequences for genome instability and evolution. Manipulating CENH3 proteins has a potential role in haploid induction, propagation of apomictic lines, reverse breeding, and creation of chromosome substitution lines. Understanding these mechanisms is important for elucidating the dynamics of centromere evolution and its role in shaping diversity.

References:

1. Malik, H. S., & Kursel, L. E. (2018). The cellular mechanisms and consequences of centromere drive. Current Opinion in Cell Biology, 52, 58-65.

2. Fishman, L., & Saunders, A. (2008). Centromere-associated female meiotic drive entails male fitness costs in monkeyflowers. Science, 322(5907), 1559-1562.

3. Higgins, D. M., Lowry, E. G., Kanizay, L. B., Becraft, P. W., Hall, D. W., & Dawe, R. K. (2018). Fitness costs and variation in transmission distortion associated with the abnormal chromosome 10 meiotic drive system in maize. Genetics, 208(1), 297-305.

4. Larracuente, A. M., & Presgraves, D. C. (2012). The selfish Segregation Distorter gene complex of Drosophila melanogaster. Genetics, 192(1), 33-53.