A linear model for quantitating the accumulation of zeins and their fractions (α+δ, β&γ) in developing endosperm of wild-type and mutant maizes

Abstract

A model based upon the occurrence of a linear relationship between the amounts of zeins and total proteins present in developing maize endosperm was applied to some data of the literature. Those were concerned with grains of W64A, Illinois high and low protein (IHP and ILP) cultured in vivo and in vitro together with in vivo grown grains of opaque-2 ( o2) and Mucronate ( Mc) mutants, and Mco2 double mutant. The relative rate of zein accumulation, corresponding to the slope of a straight line, was found to be insensitive to environmental factors. It was assessed to 0.217, 0.431, 0.490, 0.598 and 0.799 for Mco2, ILP, o2, W64A and IHP maizes, respectively. The same type of relationship was tested between the amounts of zein fractions (α+δ, β and γ) and total zeins present in developing endosperm of three genotypes. The relative accumulation rate for a given fraction was very close to its proportion determined from mature endosperm irrespective of the genotype. According to the sign of y-intercept γ-zeins were found to be synthesized prior to (α+δ)-zeins, in agreement with the analysis of protein bodies using immuno-localisation; β-zein was synthesized after (α+δ)-zeins, contrary to the findings of immuno-localisation experiments, suggesting two different accumulation rates for this fraction.