Koch, McCarty maize sugar transport paper published in ‘Nature Genetics’
A discovery regarding maize genetics has led to a new publication by Genetics Institute faculty in Nature Genetics. Masa Suzuki, Karen Koch, and Donald McCarty were co-authors on a paper detailing a discovery involving gene regulation of carbohydrate uptake in corn kernels. The paper can be accessed here.
Suzuki, McCarty and Koch are faculty members in the department of horticultural sciences and the Plant Molecular and Cellular Biology Program. Koch and McCarty are also UFGI faculty members. They collaborated with researchers at various other institutions on the project. Davide Sosso, senior research associate at the Carnegie Institution for Science, was the lead author.
“For publication, one needs to show that the association between a given mutation and a phenotype is indeed due to the hypothesized gene,” Koch said. “A good way to test this is to determine whether a different mutation to the same gene also gives the predicted phenotype. UF provided both mutants, the first one revealing the biological role, and the second one confirming the causal relationship between SWEET4 and the defective-kernel phenotype.”
“For publication, one needs to show that the association between a given mutation and a phenotype is indeed due to the hypothesized gene,” Koch said. “A good way to test this is to determine whether a different mutation to the same gene also gives the predicted phenotype. UF provided both mutants, the first one revealing the biological role, and the second one confirming the causal relationship between SWEET4 and the defective-kernel phenotype.”
During kernel development, a corn seed transports sugar into the embryo– the innermost part of the kernel– all the way through to the endosperm– the soft outer part of the kernel.
Over the past 17 years, Koch and McCarty developed a special population of corn plants for genetics research. They bred the plants so that they could easily induce and monitor mutations.
For this study, they selected plants that lacked the ZmSWEET4c gene– a gene they theorized regulated sugar transport in the kernel. They found that dysfunctional versions of the gene caused kernels to be dramatically underdeveloped. The embryo was smaller than one from an unmodified plant, and the endosperm was so shriveled it was little more than a wrinkle inside the kernel.
These results revealed that the ZmSWEET4c gene played a role in sugar uptake through the kernel.
McCarty described this gene as a “domestication” gene. As humans cultivated corn, they selected for larger and larger kernels, meaning they also inadvertently selected for versions of this gene.
However, there is some uncertainty whether bigger kernels are better.
Larger grains mean less skin, which means less fiber. Also, modern breeders sometimes neglect protein content in their pursuit of increased size.
But larger kernels can make a big difference when it comes to nourishing people for whom corn is one of their few food sources, and for feeding livestock.
The findings of this study are also significant, as they are some of the first of their kind, “[This is the] first time that a gene responsible for sugar transport has been identifiably associated with domestication,” Koch said.