VARIATION IN PROTEIN-FRACTIONS AND NITROGEN-METABOLISM OF DEVELOPING NORMAL AND OPAQUE ENDOSPERM MUTANTS OF MAIZE

Five high-lysine mutants of maize, opaque-1 (ol), opaque-9 (o9), opaqu e-11 (o11), floury-1 (fl1); and floury-3 (fl3) have been compared with the appropriate controls for their effect on endosperm growth, protei n composition, and endosperm quality related traits. All mutants with the exception of o9 and pr had a significant reduction in endosperm we ight at maturity. The o1, o11, fl3 mutants had a negative effect on th e total protein content due to a significative reduction in overall ze in content. In particular, the fl3 mutation causes a large reduction i n overall zein content to 76% of that of the wild-type due to a sizeab le reduction in all alpha-zein classes, although this reduction was gr eatest for the 22-kD alpha-zeins. In addition our data indicated that this reduction is reflected by a lower mRNA concentration in the fl3 m utant, and particularly in those mRNAs encoding the 22-kD alpha-zein c lass. The fl3 endosperm also lacks an albumin of 14-kD throughout endo sperm development. For the o1 and fl1 mutants a substantial reduction in zein level was not observed; hom ever, at maturity a significant in crease in lysine and tryptophan contents comparable to that found in o 2 mutant endosperm was measured in these mutants. No clear relationshi ps occurred between the level of four enzymes involved in N metabolism and the extent of zein repression brought about by the mutants.