02818nam a2200217 a 450000100080000000500110000800800410001910000170006024500960007726001750017352021170034865000220246565000230248765000100251065000140252065000130253465300100254765300120255765300120256970000190258114791112018-06-12       1997    bl uuuu     u00u1 u    #d1 aLOPES, M. A.  aGenetic analysis of endosperm modification in quality protein maize.h[electronic resource]  aIn: INTERNATIONAL SYMPOSIUM ON QUALITY PROTEIN MAIZE, 1994, Sete Lagoas. Quality protein maize: 1964-1994: proceedings. [S.l.]: Purdue University, 1997. p. 149-173.c1997  aA combination of genetic and biochemical analyses were used to investigate the number and mode of action of opaque-2 (o2) modifier genes and possible associations between seed modification and endosperm protein accumulation. Genetic analysis indicated the existence of two additive modifier genes in the populations studied. Analysis of 02, modified 02, their reciprocal F1's, and segregating progenies indicated that increased deposition of gamma zein, a cysteine-rich storage protein that contains no lysine, is dependent on the dosage of 02 modifier genes and directly correlated to seed modification. Molecular mapping by RFLP and Bulked Segregant Analyisis (BSA) indicated that a modifier gene maps to the same chromosomal region where gamma-zein genes are located. Analysis of recombination inbred lines with variable degrees of seed modification showed that allelic composition at the gamma-zein locus correlated with variations in endosperm modification. When we consider the possible involvement of gamma-zein in QPM endosperm modification, it is difficult to imagine that selection for increased seed modification would cause increased accumulation of a lysine-poor protein unrelated to the modification process, thus antagonizing efforts to maintain high nutritional quality. This is especially true because the selection procedures used for o2 modification placed a high priority on maintenance of seed nutritional quality. Therefore, it appears that increased accumulation of the lysine-poor gamma-zein protein was a necessary route to alter seed phenotype. Apparently, the cost of this process was a slight reduction of seed nutritional quality relative to the unmodified 02, due to increased gamma-zein accumulation. Although non-zein (lysine-containing proteins) content was found to be negatively correlated with seed density, amount of gamma-zein, and amount of total zein in the endosperm, we found that it is possible to select QPM lines with high levels of seed modification and high non-zein content. These results indicate the potential for further improvements in QPM nutritional quality.  amolecular biology  aBiologia Molecular  aMilho  aQualidade  aZea Mays  aMaize  aProtein  aQuality1 aLARKINS, B. A.