Effect of Sup-W70 o2/o2 gene on fractional composition of endosperm proteins

In our earlier paper (MGC, 1979, 53:108-111) we reported about the dominant mutation converting loose outer portions of opaque-2 endosperm into dense flint-like ones. Due to this flint shell high lysine corn improves its resistance to Fusarium diseases and low temperatures in soil at emergence (Doklady, WASHNIL, 1979, 5:3-5).

Table 1. Protein and lysine content in the endosperms of W70 line mutants
 
Genotype  Endosperm type Share of dense tissue of endosperm Protein content (%) Lysine content in protein
Integral endosperm dense part of endosperm  Integral endosperm dense part of endosperm
o2o2 sup sup floury 0.0 9.8 ±0.52 --- 3.68 ±0.046 ---
o2o2 Sup Sup modified 0.4 10.5±0.44 10.9±0.71 3.28±0.039 2.93±0.051
o2+o2+ sup sup flint-floury 0.7 11.0±0.52 11.2±0.68 2.30±0.042 2.28±0.078

The data on lysine and protein fractions distribution in different parts of a modified endosperm (Tables 1, 2) show a local specific effect of a suppressor. The major effect of the suppressor and a dominant allele of o2 gene results in intensification of zein synthesis. However, while the o2+ allele intensifies zein synthesis in an integral endosperm by 3.9 times, the suppressor in 3 doses increases it only by 2.2 times. Practically, the suppressor does not influence the total content of water-soluble proteins. The additional synthesis of zein mainly takes place in a dense portion of an endosperm for account of glutelin-3 fraction.

Table 2. Content of non-protein Lind protein nitrogen in endosperm of W70 mutants
 
Endosperm Nitrogen content
albumins & globulins zeins glutelins extractive non-extractive residue
      G1 G2 G3    
floury, integral 11.51 12.14 7.05 9.47 38.85 11.66 9.32
modified, integral 10.73 26.58 7.19 9.33 29.81 8.30 8.06
a dense part of modified endosperm 10.14 40.21 6.10 9.04 21.57 6.86 6.08
flint, integral 3.12 47.04 5.51 9.18 22.30 6.65 6.20

At the same time considering the equal concentration of lysine in protein of floury and flinty parts of an endosperm (Table 1) the dominant allele of the o2 gene manifests in a similar way in all parts of an endosperm. In contrast to the suppressor the o2+ allele hampers synthesis of albumins and globulins greatly (Table 2).

A. S. Mashnenkov


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