Synthesis of macromolecules in corn kernel mutants

All possible combinations of recessive and dominant alleles of o2, su2, Sup genes were obtained in the W70 inbred (Doklady VASHNIL, n11, 1981). Six phenotypes differing in endosperm pattern protein content and isoelectric focusing spectrum bands of zein were selected:

  1. O2/- Su2/- Sup/- flint-floury
  2. o2/o2 Su2/- sup/sup floury
  3. o2/o2 Su2/- Sup/- modified flint-floury
  4. O2/- su2/su2 Sup/- flint-glassy
  5. o2/o2 su2/su2 sup/sup glassy-floury
  6. o2/o2 su2/su2 Sup/- glassy
According to kernel weight they are distributed in the following succession: I > IV > III > II = VI > V; to density IV > I > III = V = VI > II; to protein concentration in endosperm I = III = IV = VI > II = V. No differences were found in protein concentration in whole kernels.

Alleles O2 and Sup intensify zein synthesis in I and III endosperms by 3.9 and 2.2 times respectively against genotype II. The partial reduction of the protein fractions albumins, globulins and glutelins is attributed to O2 allele effect. Sup gene displays an evident locally specific action. It occurs only in association with the o2 allele. Zein synthesis intensifies in outer flint portions of endosperm only due to the reduction of glutelin-3 fraction. Therefore an equal amount of albumins and globulins is typical for II and III endosperms. Allele su2 impedes zein synthesis and hastens glutelin-3 accumulation.

The total IEF spectrum of zein is represented by 42 components. In the endosperm of the triple homozygote V o2/o2 su2/su2 sup/sup, 16 components as a minimum have been detected. All these components are present in all endosperms, eight of them being strong and keeping their concentration, vs. weak ones varying in quantitative manifestation. Substituting su2 for Su2 in genotype II, the number of distinguished peaks in density diagrams rises to 18 due to the occurrence of protein in the middle part of the spectrum. Suppressor and allele O2 increase the number of components to 24 in genotypes III, VI and I, respectively. Up to 8 additional peaks appear in the opposite parts of the spectrum: anode and cathode.

The most valuable set of zeins is synthesized following the interaction of O2 and su2 alleles in genotype IV. Among 39 components all 24 components of genotypes III and VI are observed, but 2 components of endosperm I are absent. In the anode part of the spectrum seven absolutely new proteins in small amounts are synthesized. The behavior of su2 allele associated with O2 allele is far from the expected. It unblocks the accumulation of 17 zein proteins of acid nature in particular. In the presence of suppressor, su2 allele does not affect the number of components.

At 21 days after pollination in the endosperms of the lines, there were no differences in the concentration of total DNA, RNA, poly-A-RNA and activity of ribonuclease. With the intensification of zein synthesis and increase of zein diversity from 16 to 24 components, the process of organic matter accumulation intensifies by 1.35 times in the kernel of W70 line.

A. S. Mashnenkov

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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