02469nam a2200373 a 450000100080000000500110000800800410001910000170006024500980007726000410017530000100021650000230022652015440024965000170179365000180181065000130182865000090184165000130185065000220186365000230188565000160190865000180192465000140194265000170195665000100197365000130198365300190199665300210201565300120203665300120204865300100206065300120207065300130208214727012023-10-17       1993    bl uuuu  m   00u1 u    #d1 aLOPES, M. A.  aGenetic and biochemical characterization of the maize mutants floury-2 and modified opaque-2.  aArizona: University of Arizonac1993  a269p.  aDoctor Sc. Thesis.  aThe maize mutants floury-2 (fl2) and opaque-2 (02) reduce endosperm storage protein synthesis and lead to accumulation of protein fractions that are nutritionally more balanced. However, this advantage is offset by the soft and fragile texture of the endosperm, which gives the grain inferior quality for harvesting, storage, and processing. Further development and future usefulness of these materials may depend upon deciphering the genetic., biochemical and molecular mechanisms that affet seed physical structure and nutritional quality. The soft endosperm of the maize floury-2 (fl2) mutant is associated with a reduction in zein mRNA and protein synthesis, and enhanced levels of a 70-kD protein shown to be the maize homolog of the chaperonin BIP. An unusual alpha-zein protein of 24-kD was found to be consistently associated with the storage protein fraction from fl2 mutants. Increases in accumulation of this novel alpha-zein protein is correlated with increases in BIP accumulation and decreases in storage protein deposition. Also, an rflp that is unique to fl2 was detected with a 22-DF alpha-zein probe. the synthesis of an abnormal alpha-zein protein in fl2 could explain many features of the mutant, such as abnormal protein body morphology, BIP induction and hypostasis to 02. These findings indicate that the effects of the fl2 mutation could be a response to accumulation of a defective protein that causes impairment of secretory protein synthesis. Breeding methods based on accumulation of 02 modifier genes led (...)  abiochemistry  abiotechnology  abreeding  acorn  agenetics  amolecular biology  aBiologia Molecular  aBioquímica  aBiotecnologia  aGenética  aMelhoramento  aMilho  aZea Mays  aCaracterizacao  aCharacterization  aFlory-2  aGenetic  aMaize  aOpaco-2  aOpaque-2