As a kid that grew up among the seemingly endless fields of cash crops in southwestern Ontario, I spent a good amount of time wandering between rows of corn, usually enroute to a favourite pear tree smack in the middle of the field adjacent to my house. For some reason, I had an irrational fear of the occasional mutant ear of corn I’d encounter, usually infested with a fungus that caused the kernels to swell into grotesque shapes that oozed blue-black spores.
Minus the fungus, the odd, overly large or irregularly shaped ear was still enough to steer me away from those succulent pears. In my mind, an ear of corn was meant to be ordered in shape, arrangement, and size. The regular function of stem cells in the plant’s meristem (growing tip) also adheres to the same sense of order, resulting in ears that are relatively uniform in size, shape and kernel yield.
But this may no longer be the desired outcome. Biologists at Cold Spring Harbor Laboratory have identified a new genetic pathway responsible for controlling the ear size of corn, and have developed a technique to manipulate it, making it possible to increase the yield of a single plant by as much as 50%. Such an increase across entire fields could have an immense impact on current and future demands for food, particularly in light of global farmland loss and climate change, as was noted by several media outlets (see examples here and here).
As it turns out, the signal that controls the number of kernels that develop on an ear of corn is located not in meristem, but in the leaves of the plant. This signal can act as a brake, telling the stem cells within the meristem to stop proliferating. The research team, led by Dr. David Jackson, speculated that such a signal, coming from a more developed part of the plant, enables the plant to respond to environmental cues (light, moisture, soil quality) in order to grow only what the plant can successfully support.
Dr. Jackson and his colleagues tested the pathway by studying plants in which the pathway receptor, called FEA3, was absent or mutated. Since the signalling pathway acts as a brake, the logical thought would be that plants without FEA3 would produce large, many-kernelled ears. But this was not the case. Instead, the overabundance of seeds produced by the uncontrolled stem cells were too much for the plant to support and the end result was smaller than average ears.
But when the research team made an adjustment by creating a weak allele – essentially putting the FEA3 genetic brake on partial strength – the result was quite different and the plant was able to produce a greater but manageable increase in kernels (visible in the two right ears in the photo above). Dr. Jackson explained the research process and outcomes in the video below.
The next step will be to see if the modified braking mechanism will work with common field varieties of corn. If it does, there will be many more mutant ears in the corn fields of our future.
Image: The two maize varieties on the left combine to produce a high-yielding hybrid, center (B73/W22); hybrids grown from "weak alleles" of the FEA3 gene yield ears with significantly higher yields (the two ears on the right). Credit: Jackson Lab, Cold Springs Harbor Laboratory
It looks like a mutant, but this may be the corn of our future