Close Split of Sorghum and Maize Genome Progenitors

  1. Zuzana Swigoňová1,6,
  2. Jinsheng Lai1,6,
  3. Jianxin Ma2,3,
  4. Wusirika Ramakrishna2,4,
  5. Victor Llaca1,5,
  6. Jeffrey L. Bennetzen2,3, and
  7. Joachim Messing1,7
  1. 1Waksman Institute of Microbiology, Rutgers University, Piscataway, New Jersey 08854, USA
  2. 2Department of Biological Sciences and Genetics Program, West Lafayette, Indiana 47907, USA

Abstract

It is generally believed that maize (Zea mays L. ssp. mays) arose as a tetraploid; however, the two progenitor genomes cannot be unequivocally traced within the genome of modern maize. We have taken a new approach to investigate the origin of the maize genome. We isolated and sequenced large genomic fragments from the regions surrounding five duplicated loci from the maize genome and their orthologous loci in sorghum, and then we compared these sequences with the orthologous regions in the rice genome. Within the studied segments, we identified 11 genes that were conserved in location, order, and orientation. We performed phylogenetic and distance analyses and examined the patterns of estimated times of divergence for sorghum and maize gene orthologs and also the time of divergence for maize orthologs. Our results support a tetraploid origin of maize. This analysis also indicates contemporaneous divergence of the ancestral sorghum genome and the two maize progenitor genomes about 11.9 million years ago (Mya). On the basis of a putative conversion event detected for one of the genes, tetraploidization must have occurred before 4.8 Mya, and therefore, preceded the major maize genome expansion by gene amplification and retrotransposition.

Footnotes

  • Article and publication are at http://www.genome.org/cgi/doi/10.1101/gr.2332504.

  • 6 These authors contributed equally to this work.

  • 3 Present address: Department of Genetics, University of Georgia, Athens, GA 30602, USA

  • 4 Present address: Department of Biological Sciences, Michigan Tech University, MI 49931, USA

  • 5 Present address: Analytical and Genomic Technologies, Crop Genetics R&D, DuPont Agriculture & Nutrition, Wilmington, DE 19880, USA.

  • 7 Corresponding author. E-MAIL messing{at}waksman.rutgers.edu; FAX (732) 445-0072.

    • Accepted April 6, 2004.
    • Received January 4, 2004.
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