"QPM has made strides in overcoming malnutrition in these populations, but to make it more available to people who need it, modern approaches to breeding called 'marker-assisted breeding' will be superior in adapting local corn varieties for these people," said Messing, who is also director of the Waksman Institute of Microbiology.
As part of the investigation, Rutgers postdoctoral researcher Yongrui Wu used a technique to eliminate, or "knock out," the expression of the genes that geneticists suspected were involved in QPM kernel hardness. After knocking out these two genes, responsible for producing proteins known as gamma zeins, Wu observed softer kernels in the offspring.
Detailed investigation of original and knockout kernels using electron microscopy revealed that soft kernels lacked a proteinaceous matrix interconnecting starchy components while providing structural integrity. Such structures were not present in the knockout offspring. The researchers therefore pegged the gamma zeins regulated by these two genes, labeled 16- and 27-kDa gamma zein, as key components of this molecular structure and, as a result, QPM's hardness.
The softer, commercially unsuccessful hybrid from 1960 had higher levels of lysine and tryptophan because it had reduced levels of several categories of zein proteins, which conferred kernel hardness but crowded out other proteins that carried lysine and tryptophan. QPM has the gamma zeins responsible for the hardness-preserving structure while still lacking other zeins that crowded out nutritional proteins.
|Contact: Carl Blesch|