COLD SPRING HARBOR, N.Y.,
Aug. 7, 2024 /PRNewswire/ -- Cold
Spring Harbor Laboratory (CSHL) has begun to unravel a mystery
millennia in the making. Our story begins 9,000 years ago. It was
then that maize was first domesticated in the Mexican lowlands.
Some 5,000 years later, the crop crossed with a species from the
Mexican highlands called teosinte mexicana. This resulted in
cold adaptability. From here, corn spread across the
continent, giving rise to the vegetable that is now such a big part
of our diets. But how did it adapt so quickly? What biological
mechanisms allowed the highland crop's traits to take hold? Today,
a potential answer emerges.
CSHL Professor and HHMI Investigator Rob
Martienssen had been studying RNA interference, the
process of small RNAs silencing genes, for more than 20 years when
University of Wisconsin researcher
Jerry Kermicle reached out with a
curious observation. His experiments crossing semi-sterile teosinte
hybrids with traditional maize had caused their offspring to behave
very unusually. With normal inheritance, the offspring should have
eventually become completely sterile or fertile. But no matter how
many times Kermicle crossed the hybrids with maize, all the
offspring were semi-sterile, too. What was happening?
To figure it out, Martienssen and graduate student Ben Berube sequenced the genomes from hundreds
of pollen grains of the semi-sterile offspring. They discovered the
same sections from the teosinte genome were present in each.
Martienssen says:
"There were two pieces of the genome, one on chromosome 5 and
one on chromosome 6, that were always inherited. That told us the
genes responsible must be in those regions."
On chromosome 5, they found that a gene called Dicer-like
2 makes a group of small RNAs that are always in
semi-sterile hybrids but not traditional maize. With that finding,
the Martienssen lab was able to pinpoint what they call Teosinte
Pollen Drive (TPD). This "selfish" genetic system
eliminates competing pollen grains that lack the gene drive. It
causes maize-teosinte hybrids to pass certain traits through males
more often than females. The discovery could have significant
implications for the agriculture industry. But in Martienssen's
eyes, the finding is even bigger than its potential weed control
applications:
"I'm more excited by the evolutionary aspects, what it might
mean for the process of domestication, and how it could have been
much quicker than we thought."
If teosinte mexicana is "the Neanderthal of maize,"
Martienssen may have found in TPD corn's "missing link." The
breakthrough could explain how corn came to thrive across
America—but also why certain small RNAs are so common in plant and
animal sperm cells, including ours.
About Cold Spring Harbor Laboratory
Founded in 1890, Cold Spring Harbor Laboratory has shaped
contemporary biomedical research and education with programs in
cancer, neuroscience, plant biology and quantitative biology. Home
to eight Nobel Prize winners, the private, not-for-profit
Laboratory employs 1,000 people including 600 scientists, students
and technicians. For more information, visit www.cshl.edu.
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SOURCE Cold Spring Harbor Laboratory