Elucidation of zein isoforms associated with high protein quality traits for targeted improvement in maize-based nutrition

Background and ObjectivesZein proteins of maize endosperm are nutritionally poor, but important for vitreous kernel texture. The Opaque-2 mutation enhances the protein quality but downregulates zein expression, distorting the kernel texture. Quality protein maize (QPM) is nutritionally improved, hard endosperm maize developed by introgression of endosperm modifiers under an opaque-2 background. The present study aims to analyze the variability in zein expression patterns in normal, opaque-2, and QPM lines through sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis analyses.FindingsResults revealed that the total number of zein isoforms is almost similar in opaque-2, normal, and QPM lines. Overall, in this study, it is concluded that the opaque-2 mutation specifically affects the expression of high-molecular-weight zeins, which are being counterbalanced by the expression of low-molecular-weight zein isoforms and nonzein proteins.ConclusionGenomic data retrieval studies revealed the possible presence of multiple 27 kDa isoforms with varied isoelectric points (pI), which is a subject for further investigation. The differential expression of 15 kDa zein in QPM emerged as a novel player in endosperm modification.Significance and NoveltyThe present study provides insight into the diversified expression of zeins in different maize types. The variable isoform expression has the potential to generate stable QPM lines by targeting effective isoforms, ensuring endosperm modification without hampering the nutritional quality.