ViPS Invited Seminar January 2024

Jeffrey Ross-Ibarra, University of California, Davis, USA

Date: 17th January 2024

Time: 13:00

Title: Admixture, alleles, and the origins of maize

Location: Seminar room 228, Lab building, Koetilantie 5

Host: Tanja Pyhäjärvi

Abstract: The widely accepted narrative of maize domestication posits a single origin from the wild grass Zea mays ssp. parviglumis in southwest Mexico, likely beginning with de novo mutation at an important gene controlling kernel architecture. However, recent genomic surveys challenge this simplicity, revealing evidence of gene flow from another wild relative, Zea mays ssp. mexicana. Here we demonstrate widespread admixture between maize and Zea mays ssp. mexicana across time and geography, suggesting a revised model of maize origins in which maize hybridized with Zea mays ssp. mexicana in the central Mexican highlands around 4000 years post-domestication.  We also revisit the origin of the important domestication tga1, using population genetic analysis and simulations to show that relevant diversity at this key locus likely predated domestication, highlighting the importance of adaptation from standing genetic variation. Together, our findings challenge existing models of crop evolution and illustrate domestication as a complex evolutionary process rather than a single event.

Jeffrey's lab works on plant evolutionary genetics, with a focus on maize and its wild relatives. We use population and quantitative genomics approaches to investigate questions including local adaptation, co-evolution, and the evolution of the genome.

Read more about Jeffrey's work

Related publications:

Mei, W., M. G. Stetter, D. J. Gates, M. C. Stitzer, and J. Ross-Ibarra. 2018. Adaptation in plant genomes: Bigger is different. American Journal of Botany 105(1): 16–19. doi: 10.1002/ajb2.1002

Anderson SN, Stitzer MC, Brohammer AB, Zhou P, Noshay JM, O'Connor CH, Hirsch CD, Ross-Ibarra J, Hirsch CN, Springer NM. Transposable elements contribute to dynamic genome content in maize. Plant J. 2019 Dec;100(5):1052-1065. doi: 10.1111/tpj.14489.

Julia Engelhorn, Samantha J. Snodgrass, Amelie Kok, Arun S. Seetharam, Michael Schneider, Tatjana Kiwit, Ayush Singh, Michael Banf, Merritt Khaipho-Burch, Daniel E. Runcie, Victor Sánchez Camargo, J. Vladimir Torres-Rodriguez, Guangchao Sun, Maike Stam, Fabio Fiorani, James C. Schnable, Hank W. Bass, Matthew B. Hufford, Benjamin Stich, Wolf B. Frommer, Jeffrey Ross-Ibarra, Thomas Hartwig. Phenotypic variation in maize can be largely explained by genetic variation at transcription factor binding sites. bioRxiv 2023.08.08.551183; doi:

Ning Yang et al.Two teosintes made modern maize.Science 382,eadg8940 (2023) DOI:10.1126/science.adg894

Chen, L., Luo, J., Jin, M. et al. Genome sequencing reveals evidence of adaptive variation in the genus Zea. Nat Genet 54, 1736–1745 (2022).