Despite the improvement in lysine composition and nutritional value, mosto2lines were not commercially developed, due to their low grain yields, soft, chalky endosperm, and insect susceptibility. To solve those problems, breeders developed modified o2 lines by introgressing genes that alter the soft and opaque endosperm, producing a hard and vitreous endosperm while maintaining highly sine content of o2 lines. Those genes were designated o2 modifiers, and theo2 lines with those genes are called Quality Protein Maize. However, it is time-consuming to develop QPM lines, because of the difficulty of introducing multiple mo2loci, while simultaneously maintaining the amino acid level in kernels. Improvement of QPM would be easier if the key mechanisms by which Allopurinol themo2genesproduce a hard and vitreous endosperm were characterized, but so far, the location of each modifier gene and their specific downstream effects are not well understood. Genetic mapping of mo2 revealed the link age between a locus close to the centromere of chromosome 7and the gene encoding 27-kD ��-zein. QPMs maintain the reduced level of 22-kD ��-zein aso2 mutants, but accumulate twice to three times as much 27-kD ��-zein as wild type and unmodified o2 lines.A dominant RNAi transgene was introduced into QPM lines to eliminate the expression of the gene encoding 27-kD ��-zein, resulted in a nopaquepheno type in RNAi treated QPM endosperm. Therefore, 27-kD ��-zein was believed to be an essential component of QPM endosperm modification associated with the vitreous phenotype. Additionally, genome-wide Quantitative Trait Locus mapping and expression analysis identified several loci and genes associated with the vitreous phenotype of QPM, including glucose transporter, ��-subunit of pyrophosphate-dependent fructose-6-phosphate 1-phospho GW791343 hydrochloride transferase and ethylenein sensitive 3-like protein. And recent study showed that PFP�� was coinduced with heat shock proteins, which regulates the redox energy balance in QPM lines. Apart from zeins, starch granule synthesis and structure may also influence the endosperm texture.