Abstract Detail

A Botanist at the Extreme: Honoring the great contributions of Dr. Vicki A. Funk

Rieseberg, Loren [1].

Exploring two mysteries of chromosomal evolution in plants.

Chromosomal rearrangements are abundant in plants. Many of these rearrangements are thought to be highly deleterious, so how they become established represents a long-standing mystery in evolutionary biology. A less well-known puzzle concerns the non-random distribution of chromosomal rearrangements within genomes. In my presentation, I will summarize information about chromosomal evolution from Helianthus sunflowers and other members of the Asteraceae family to argue that consideration of natural selection and constraint can largely resolve these puzzles. For instance, my lab has recently shown that many large structural variants (mostly inversions) in wild sunflowers are favored by natural selection because they suppress recombination between locally adapted alleles. Furthermore, such variants appear to be clustered in the genome. This is likely due to the same process, in which additional locally adapted alleles are added to the gene module protected by the original structural variant. We also have found that large-scale translocations repeatedly involve the same chromosomes and even the same chromosomal regions, especially centromeres. The association between large translocations and centromeres is probably due to centromere drive, in which a transmission advantage of the translocated chromosome permits its establishment despite negative effects on fertility. Although I contend that the dynamics of large structural variants in plant populations are likely driven by selection, this doesn’t rule out a role for genetic drift in the establishment of the thousands of smaller structural differences distinguishing species.

1 - University Of British Columbia, Department Of Botany, 6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada

Keywords:
Helianthus
Chromosomal Rearrangements
structural-changes
Inversions.

Presentation Type: Symposium Presentation
Number: S4003
Abstract ID:173
Candidate for Awards:None