The maize (Zea mays) aleurone layer occupies the single outermost layer of the endosperm. The defective kernel1 (dek1) gene is a central regulator required for aleurone cell fate specification. dek1 mutants have pleiotropic phenotypes including lack of aleurone cells, aborted embryos, carotenoid deficiency, and a soft, floury endosperm deficient in zeins. Here we describe the thick aleurone1 (thk1) mutant that defines a novel negative function in the regulation of aleurone differentiation. Mutants possess multiple layers of aleurone cells as well as aborted embryos. Clonal sectors of thk1 mutant tissue in otherwise normal endosperm showed localized expression of the phenotype with sharp boundaries, indicating a localized cellular function for the gene. Sectors in leaves showed expanded epidermal cell morphology but the mutant epidermis generally remained in a single cell layer. Double mutant analysis indicated that the thk1 mutant is epistatic to dek1 for several aspects of the pleiotropic dek1 phenotype. dek1 mutant endosperm that was mosaic for thk1 mutant sectors showed localized patches of multilayered aleurone. Localized sectors were surrounded by halos of carotenoid pigments and double mutant kernels had restored zein profiles. In sum, loss of thk1 function restored the ability of dek1 mutant endosperm to accumulate carotenoids and zeins and to differentiate aleurone. Therefore the thk1 mutation defines a negative regulator that functions downstream of dek1 in the signaling system that controls aleurone specification and other aspects of endosperm development. The thk1 mutation was found to be caused by a deletion of approximately 2 megabases.
Methionine is a nutritionally limiting amino acid in poultry diets based on maize (Zea mays L.) grain. Synthetic dietary supplements are available but are costly and not preferred by organic poultry producers. The development of high methionine maize varieties would reduce the need for supplementation. Several approaches have been reported for achieving this goal. Here, we report a novel approach that can produce diverse inbred lines with higher content of methionine than other methods. Inbred lines were developed using doubled haploid technology from a broad-based synthetic population that has undergone mass selection for grain methionine concentration.Out of 18 randomly selected inbred lines, one was significantly higher in methionine concentration than the high methionine check and 11 were not significantly different from it. The inbred lines developed in this way also exhibited useful genetic diversity for several agronomic and kernel quality traits, including flowering date, and orangeness of the kernel. This approach is an excellent complement to other breeding methods for development of varieties for production of poultry feed. Because the approach does not rely on transgenic technology, the resulting lines are suitable for use by organic producers and are well suited to organic production systems.
Cereal Chem. 91(2):183-188Oats (Avena sativa L.) have received significant attention for their positive and consistent health benefits when consumed as a whole grain food, attributed in part to mixed-linkage (1-3,1-4)-β-D-glucan (referred to as β-glucan). Unfortunately, the standard enzymatic method of measurement for oat β-glucan is costly and does not provide the high-throughput capability needed for plant breeding in which thousands of samples are measured over a short period of time. The objective of this research was to test a microenzymatic approach for high-throughput phenotyping of oat β-glucan. Fifty North American elite lines were chosen to span the range of possible values encountered in elite oats. Pearson and Spearman correlations (r) ranged from 0.81 to 0.86 between the two methods. Although the microenzymatic method did contain bias compared with the results for the standard streamlined method, this bias did not substantially decrease its ability to determine β-glucan content. In addition to a substantial decrease in cost, the microenzymatic approach took as little as 6% of the time compared with the streamlined method. Therefore, the microenzymatic method for β-glucan evaluation is an alternative method that can enhance high-throughput phenotyping in oat breeding programs.
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