02208nam a2200253 a 450000100080000000500110000800800410001910000170006024501180007726001590019552014120035465000220176665000230178865000180181165000140182965000140184365300170185765300160187465300130189065300120190365300080191565300120192370000190193514787702018-07-13       1990    bl uuuu     u00u1 u    #d1 aLOPES, M. A.  aGenetic regulation of modified protein composition in hard-endosperm opaque-2 maize (QPM).h[electronic resource]  aIn: INTERNATIONAL CONFERENCE ON SORGHUM NUTRITIONAL QUALITY, 1990, West Lafayette. Proceedings. West Lafayette: Purdue University, 1990. p. 142-154.c1990  aOpaque-2 (o2) is a mutation of one of the regulatory loci that control storage protein gene expression in maize endosperm. It results in a drastic reduction in the prolamine content of the seed, which impacts on the nutritional quality. The soft endosperm associated with this mutation is probably a consequence of the low amounts of these proteins, although the relationship between the reduction in prolamine content and this phenotype is not weel understood. Qaulity Protein Maize (QPM) seeds are opaque-2 genotypes with a high frequency of "modifier genes" that confer a normal, vitreous phenotype to the endosperm, while maintaining high levels of lysine and tryptophan in the protein. As in the soft endosperm opaque-2 mutant, the improved nutritional quality of QPM genotypes is due to a higher percentage of the non-zein fraction which is nutritionally more balanced than the zein proteins. However, the storage protein of QPM contains a pronounced increase in the amount of the Mr 27,000 gamma-zein as compared to normal, unmodified, opaque-2 genotypes. The synthesis of this protein is not regulated by the opaque-2 (o2) loci. Our studies with normal, soft endosperm opaque-2, and opaque-2 QPM genotypes, individually and in combination, suggest that there may be a relationships between the high synthesis of this zein protein (Mr 27,000) and modification of kernel structure in mutant genotypes.  amolecular biology  aBiologia Molecular  aBiotecnologia  aProteína  aQualidade  aBiotecnology  aMilho opaco  aOpaque 2  aProtein  aQPM  aQuality1 aLARKINS, B. A.