D. V. Glover

Endosperm Protein Synthesis in Maize Mutants with Increased Lysine Content

The endosperm proteins of the maize mutants, opaque-2, opaque-7, floury-2, brittle-2, and the double mutant of opaque-2 and brittle-2, were separated into five soluble fractions by the Landry-Moureaux method. As compared to their isogenic normal counterparts, the mutant endosperms had higher concentrations of albumins, globulins, and glutelin-3, and lower concentrations of prolamines. The combination of the opaque-2 and brittle-2 genes enhanced this difference. Although the four mutant genes are located on three different chromosomes, they exert a similar effect on endosperm protein composition. Five other starchmodifying mutants with high lysine content resemble the brittle-2 mutant in endosperm protein composition, when the gene is present either singly or combined with opaque-2. Therefore, the pattern of protein synthesis in all maize mutants with high lysine concentrations may be either identical or very similar. Because no synergistic effect on lysine concentration is obtained when floury-2 is combined with opaque-2, different pathways leading to reduced zein synthesis may exist in the floury and starch-modifying mutants with high lysine concentrations.

Structural and Physicochemical Properties of Endosperm Starches Possessing Different Alleles at the Amylose-extender and Waxy Locus in Maize (Zea mays L.)

The structure and some physicochemical properties of endosperm starches from seven amylose-extender (ae) and two waxy (wx) alleles of maize (Zea mays L.) were studied. Starches prepared from mature kernels of six ae mutants, Oh43 inbred line ae (standard ae), ae-RWB-2 and ae-RWB-3, and W23 x L317 hybrid line ae-PP, ae-Bol 561 and ae-emll, were uniquely ae type, as was concluded from B type X-ray diffractograms; high gelatinization temperatures determined by differential scanning calorimetry (DSC); with poor starch-granule digestibility to amylase; high amylose (37-45 %) and high intermediate fraction (13-18%) contents; and low ratios (1.0-1.2) of long α-1,4-chains to short α-1,4-chains of amylopectin determined by gel permeation chromatography (GPC) of isoamylase-debranched starches. The results also indicated that different ae alleles had different effects on the amylose content of endosperm starches. Mature kernels of Oh43 ae-RWB-1 mutant showed tarnished and translucent phenotype characteristics of the ae genotype but contained endosperm starch with 21-22% of amylose which was lower than that of the Oh43 normal counterpart. Both wx-B and wx-C (standard wx) genes have similar effect on structure and physicochemical properties of waxy starches of A632, B37, C105, Oh43, and W64A inbred lines.

The genetic effects on some physico-chemical properties of starch granules

Publisher Summary The properties of starch from plants mainly depend on plant species and genetic factors. The shape, size, crystallinity, gelatinization temperatures, enzymatic susceptibilities, amylose contents, and chain-length distributions of amylopectins of starch granules differ for various genotypes and plant species. This chapter explores the study of some properties of commercial starches (with defined sources) of several plant species, and normal type (wild type) and two kinds of mutant maize starches, so that genetic effects and the effect of plant species on the properties of starch can be identified.. The chapter also illustrates the differences in the unit-chain length distributions of debranched amylopectins in starches of several plant species with comparison to normal maize amylopectin by HPAEC-PAD. Subsequently, the chapter summarizes some physico-chemical properties of starches of several plant species. The peak temperature of gelatinization of the ae maize starch determined by DSC was higher and that of su2 maize starch was lower than that of the other starches. The peak viscosity measured by RVA and swelling power of potato and sweet potato starches were higher than those of cereal starches. The results indicate that the hot water absorption ability of starch granules of sweet potato and potato is larger than cereal starch granules. Moreover, the viscosity potato and sweet potato starch is higher than those of cereal starches. The peak viscosity (RVA) and swelling power of the ae starch granules were lower than those of other starches.