Researchers discover how corn aligns
Associated Press
03/05/06
Plants with inactive gene grow crooked kernels
AMY LORENTZEN
Associated Press
AMES, Iowa - You sink your teeth into an ear of crisp, yellow corn-on-the-cob, its
perfect rows of kernels bursting in your mouth.
Now imagine if all those kernels were instead twisted into a messy patchwork,
making it more difficult to enjoy.
"You wouldn't be able to eat them row by row," joked Erik Vollbrecht, a
professor in the Department of Genetics, Development and Cell Biology at
Iowa State University. He spent four years studying what keeps the kernels
aligned evenly in their rows.
Vollbrecht was a member of a group of researchers at Cold Spring Harbor
Laboratory in New York that identified the gene ramosa1, which affects the
architecture of corn - how kernels and tassels branch out from the cob.
In cobs with active ramosa1, the kernels grow from tiny branches, creating
straight rows on a compact cob and delivering higher yields. In corn where the
gene is inactive, there can be more and longer branches, and kernels grow in
loose, crooked rows. Those branches take space away from kernel growth,
resulting in a larger cob that requires more energy to grow.
As he held up a gnarly looking corn specimen, Vollbrecht said the extra branches
would make corn "a nightmare to process."
The researchers' inspiration for the project was an unusual ear of corn harvested
in 1909 from an Illinois farm field. The deformed cob - its rows crisscrossing like
a tangled ball of beads - had inactive ramosa1. It was so strange-looking, the
industry thought at first that the mutant ear was a new species of maize, said
Robert Martienssen, the lead researcher on the ramosa1 project.
His team recreated the discovery by producing a new mutant cob. They used
"jumping genes" that tagged the ramosa1 gene, allowing them to isolate the gene
and study its DNA. The endeavor was much like finding a needle in a haystack.
Martienssen had to walk through a field of 50,000 plants to find the new cob that
had inactive ramosa1.
"As you might imagine, I was very excited when I found that plant and recovered
the pollen and the seed," Martienssen said.
Martienssen and his crew revealed their ramosa1 findings last year in the August
25 issue of Nature. They unveiled findings this week on ramosa2 - a gene that
also regulates corn architecture and works along with ramosa1.
Vollbrecht said ancient farmers - as far back as 10,000 years ago - selected
ramosa1 traits when breeding the wild grass teosinte into domesticated corn.
The researchers' hypothesis is that as the ears of corn grew from just two rows of
kernels to more rows, they needed more ramosa1. The prehistoric farmers
caught onto this and "we found they selected for very specific versions of this
gene," Vollbrecht said.
With the discovery, researchers now know that all modern varieties of corn share
the same ramosa1 gene, and Martienssen said that information can be used to
introduce new versions of the gene to improve corn and possibly increase yields.
An added plus is that ramosa1 influences tassel branches, the part of the plant
that produces pollen.
Because only a few tassel branches are needed, researchers could develop corn
with fewer of them so that the plant doesn't have to devote as much energy to
pollen production.
"We might also be able to use it in other crops, such as sorghum, wheat and rice,
where branching may be beneficial," Martienssen said.