Elucidating the changes in proteins and metabolites of different maize varieties due to domestication

Breeders have performed selective breeding over the years to turn maize from its wild ancestor, teosinte, into its modern variety (Zea mays). Some health-beneficial compounds might be lost in the process. Here, we aim to understand the potential changes in the protein and metabolites in maize due to domestication by conducting a comparative study between 26 modern maize, 25 landraces, and 25 teosinte varieties. We looked at the protein content of all the ground undigested maize lines by the BCA kit assay. The average protein level in teosinte lines was three times higher than that of modern maize and landraces. Analyzing the metabolite profile of the undigested maize lines, we found that the relative levels of quinic acid, mucic acid, caffeic acid, and chlorogenic acid were high in teosinte, but sugars were more abundant in modern maize. The samples were processed using simulated gastrointestinal digestion to understand the impact of domestication on the digestibility of maize proteins. Post-digestion, there was no significant difference in the peptide quantity between the teosinte, landrace, and modern maize groups, as measured by the fluorescent peptide assay kit. A high peptide content for modern maize and landraces could be due to their better degree of hydrolysis (digestibility), determined by the OPA technique. While the average digestibility for modern maize and landraces was 72.37% and 42.09%, respectively, it was only 15.13% for teosinte. However, the results from the anti-oxidation activity assay, involving all the maize lines using gastrointestinal cells, show that teosinte lines have higher antioxidative activity, ranging from 9.1 – 31.6 %. The antioxidative properties in digested teosinte samples might be due to bioactive peptides, which shall be confirmed by investigating their peptide profiles. This unique work at deciphering the functional changes in maize can guide us in producing maize hybrids with enhanced protein quality.