UH genetic researchers contribute to new corn genome sequence

University of Hawaiʻi at Mānoa
Gernot Presting, (808) 956-8861
Professor, Molecular Biosciences and Bioengineering
Posted: Jun 15, 2017

Centromeres on three corn chromosomes.
Centromeres on three corn chromosomes.

UH Mānoa Professor Gernot Presting and two postdoctoral scholars in his lab, Kevin Schneider and Thomas Wolfgruber, are contributors to an historic release of a new, high-quality corn reference genome sequence that shows reasons why corn can be adapted to a wide variety of growing conditions. The seed corn industry is an important component of the Hawaiian economy.

Researchers at the Cold Spring Harbor Laboratory in New York and the U.S. Department of Agriculture led the sequencing effort that involved laboratories at the University of California at Davis, University of Georgia, University of Minnesota and technology companies Pacific Biosciences and BioNano Genomics. Their findings have been published in the journal Nature at http://www.nature.com/nature/journal/vaop/ncurrent/full/nature22971.html.

Importantly, this genome assembly includes high-quality sequence of many corn centromeres. On the X-shaped chromosome, the centromere is at the “cross” point of the two arms. Like the rest of the chromosome, centromeres are composed of double-stranded DNA and protein, but have been very difficult to sequence because they are composed of highly repetitive DNA.

The corn genome is stored on ten chromosomes and consists of about 2.4 billion nucleotides that contain the instructions for making a corn plant. Genome analysis has become an indispensable tool for plant improvement by breeding. The newly released sequence fills in ~100,000 gaps left in the initial genome sequence released in 2009. This additional information leads to a much fuller understanding of the genetic structure of this culturally and economically important crop. Most significantly, the findings show that the corn genome is very “flexible” or adaptable. This flexibility will have potential benefits in the advent of climate change.

Recent advances in sequencing technology played a major role in making this improvement possible. Members of the Presting laboratory in the Department of Molecular Biosciences and Bioengineering, College of Tropical Agriculture and Human Resources, have previously demonstrated the potential of these methods to determine the nucleotide sequence of corn centromeres.

Centromeres play an essential role in cell division by ensuring that each new cell obtains a complete set of chromosomes. They act as attachment sites for the ropes (spindle microtubules) that separate chromosomes during cell division, thus ensuring that each daughter cell obtains a complete set of instructions. Chromosomes without centromeres are lost, and chromosomes with more than one centromere can fragment during cell division. Surprisingly, most centromeres of domesticated corn contain much less genetic variation than the chromosome arms, indicating heavy selection for specific centromere types. Schneider, Wolfgruber and others in the Presting laboratory, who have studied the centromeres of corn for the past 12 years, were instrumental in resolving these regions in the new corn genome assembly.

Said Presting, “This new genome has already been tremendously useful in confirming and extending our understanding of centromere evolution deduced from earlier genome assemblies, and will undoubtedly help us clarify the function of the repetitive DNA that is typical of centromeres.”

For more information, visit: https://cms.ctahr.hawaii.edu/mbbe/