In corn reproduction, male flowers at the top of the plants distribute pollen grains two at a time through individual tubes to tiny cobs on the stalks covered by strands known as silks in a process known as double fertilization. When the two pollen grains come in contact with an individual silk, they produce a seed containing an embryo and endosperm. Each embryo results in just a single kernel of corn, said Diggle.
The team took advantage of an extremely rare phenomenon in plants called "hetero-fertilization," in which two different fathers sire individual corn kernels, said Diggle, currently a visiting professor at Harvard. The manipulation of corn plant genes that has been going on for millennia -- resulting in the production of multicolored "Indian corn" cobs of various colors like red, purple, blue and yellow -- helped the researchers in assessing the parentage of the kernels, she said.
Wu, who cultivated the corn and harvested more than 100 ears over a three-year period, removed, mapped and weighed every individual kernel out of each cob from the harvests. While the majority of kernels had an endosperm and embryo of the same color -- an indication they shared the same mother and father -- some had different colors for each, such as a purple outer kernel with yellow embryo.
Wu was searching for such rare kernels -- far less than one in 100 -- that had two different fathers as a way to assess cooperation between the embryo and endosperm. "It was very challenging and time-consuming research," said Friedman. "It was like looking for a needle in a haystack, or in this case, a kernel in a silo."
Endosperm -- in the form of corn, rice, wheat and other crops -- is critical to humans, providing about 70 percent of calories we consume annually worldwide. "The tis
|Contact: Pamela Diggle|
University of Colorado at Boulder