Mucronate, Mc, a dominant gene of maize which interacts with opaque-2 to suppress zein synthesis

Abstract

This paper describes a new dominant mutation of maize, Mc, which interferes in the endosperm with the synthesis of storage proteins. The mutant is characterized by an opaque phenotype; it reduces the deposition of zein and it increases the level of methionine. The mutation is specifically related to storage protein synthesis since soluble and insoluble carbohydrates are present at normal levels. The main interest of this mutant lies in its synergistic interaction with opaque-2 in repressing zein synthesis. In the double mutant o2Mc the accumulation of zein is reduced to less than 10% of that of the normal endosperm. The control on zein synthesis exerted by the double mutant is at the level of production or stability of translatable zein mRNAs. The double mutant o2Mc germinates well offering the opportunity of using it in biochemical and molecular studies related to storage protein synthesis; the reduced endosperm weight of o2Mc negates its practical utilization in breeding maize for quality.

Assessment of protein nutritional quality and effects of traditional processes: A comparison between Ethiopian quality protein maize and five Ethiopian adapted normal maize cultivars

“…Analysis of various maize germ plasm samples revealed a broad range of variability for lysine content, which was 1.6-2.6 g per 100 g of protein for normal varieties and 2.8-4.5 g per 100 g of protein for opaque-2 [34][35][36][37]. There were other accompanying changes in the proportions of other amino acids in QPM BH542, which are similar with the type of modifications reported in the amino acids profile of opaque-2 [38,39]. In addition to lysine and tryptophan, the contents of aspartic acid, threonine, glycine, cysteine, valine, histidine, and arginine were higher in QPM BH542 while the levels of glutamic acid, alanine, leucine, tyrosine, phenylalanine decreased sharply, compared to that of normal maize varieties.…”

The maize Mucronate mutation is a deletion in the 16‐kDa γ‐zein gene that induces the unfolded protein response1

“…size, shape and the fact that A188 has white kernels) of the three different genetic backgrounds (A188, B73 and PHR03; see ). Because earlier studies (Salamini et al. , 1983) indicated a gene dosage effect of the Mc mutation on the manifestation of the opaque phenotype, the T1 events were propagated in the field and self‐pollinated.…”

“…Subsequent studies suggested that Mc is a dominant mutation that reduces the synthesis of zein storage proteins. Although a single copy of the mutant allele was sufficient to confer an opaque kernel phenotype, two doses were required to reduce zeins to levels comparable with a homozygous (three doses) mutant (Salamini et al. , 1983).…”

A Defective Signal Peptide Tethers the floury-2 Zein to the Endoplasmic Reticulum Membrane

“…Defective endosperm B-30 and Mucronate, two other endosperm-specific mutants, have phenotypes similar to f12 with respect to elevated molecular chaperone levels, altered protein body morphology, and dominance of mutant over normal alleles. These mutants also possess zeins with altered electrophoretic mobility through SDS-polyacrylamide gels (Salamini et al, 1983; J.W. Gillikin and R.S.…”