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Hernández-Rodríguez, M., Babu, R., Skinner, D. J., Palacios‐Rojas, N., Martins, M. C. M., García-Zavala, J. J., Lobato-Ortíz, R., Santacruz-Varela, A., Castillo-González, F., Xu, Y., & Prasanna, B. M. (2022). Desarrollo de marcadores para mejoramiento de maíz con proteína de calidad y estudio de interacción entre los genes Opaco-2 y Ask2. Revista Fitotecnia Mexicana, 45(3), 293-302. https://doi.org/10.35196/rfm.2022.3.293
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Los granos de maíz de alta calidad proteica (QPM) contienen el doble de lisina y triptófano en comparación con los granos de maíz normales. Aunque la mutación opaco-2 (o2) es la causa subyacente de este cambio beneficioso, otros genes como la aspartato quinasa-2 (Ask2) afectan en menor grado el contenido de aminoácidos en el endospermo. Hasta el momento, los informes sobre la interacción entre ambos loci son escasos y no existen ensayos de alto rendimiento para la identificación de los alelos de estos genes. Los objetivos de esta investigación fueron: 1) estudiar la interacción entre los genes o2 y Ask2 con respecto a la acumulación de aminoácidos en el endospermo de una población F2, 2) identificar SNPs conservados en el gen o2 que puedan ser utilizados como marcadores, 3) estimar la frecuencia de un SNP de Ask2, asociado con la acumulación de lisina en el endospermo, en germoplasma del CIMMYT, y 4) desarrollar ensayos de marcadores de alto rendimiento para estos SNPs. El estudio de interacción mostró un efecto preponderante del o2 sobre la acumulación de 11 aminoácidos (P ≤ 0.01). Al parecer, Ask2 solamente actúa con o2 para mejorar marginalmente los niveles de lisina, histidina y metionina en los homocigotos recesivos dobles. La secuenciación de amplicones en el locus o2 condujo a la identificación de un SNP en el exón 1 que discriminó todos los genotipos QPM (C) de los genotipos no QPM (T). La validación de este SNP a través de los ensayos KASP™ indicó que fue 92 % asertivo en la diferenciación de los genotipos o2. En contraste, la frecuencia del SNP de Ask2 en el germoplasma QPM del CIMMYT fue baja; sin embargo, un marcador SSCP desarrollado utilizando este SNP detectó cinco variantes, lo que indica que otros cambios de base desconocidos pueden conferir respuestas positivas de aumento de lisina. Estos marcadores podrían ayudar a la selección asistida en variedades QPM.
Quality Protein Maize (QPM) kernels contain twice the amounts of lysine and tryptophan compared to normal corn kernels. Although the opaque-2 (o2) mutation is the underlying cause of this beneficial change, other genes such as Aspartate kinase-2 (Ask2) affect the amino acid content in the endosperm to a lesser degree. To date, reports on the interaction between both loci are scarce and there are no high-throughput assays for the identification of the alleles of these genes. The objectives of this research were: 1) to study the interaction between the o2 and Ask2 genes with respect to the accumulation of amino acids in the endosperm in an F2 population, 2) to identify conserved SNPs into the o2 gene that can be used as markers, 3) to estimate the frequency of an SNP of Ask2 associated with the accumulation of lysine in the endosperm in CIMMYT germplasm, and 4) to develop high-throughput marker assays for these SNPs. The interaction study showed a preponderant effect of o2 on the accumulation of 11 amino acids (P ≤ 0.01). Ask2 appeared only to act with o2 to enhance marginally lysine, histidine and methionine levels in the double recessive homozygotes. Sequencing of amplicons at the o2 locus led to the identification of an SNP in exon 1 that discriminated all QPM (C) genotypes from non-QPM (T) genotypes. Validation of this SNP through KASP™ assays indicated that it was 92 % assertive in differentiating the o2 genotypes. In contrast, the frequency of the Ask2 SNP in CIMMYT QPM germplasm was low; however, an SSCP marker developed using this SNP detected five variants indicating that other unknown base changes may confer positive lysine-increasing responses. These markers could aid the marker-assisted selection of QPM cultivars.
Quality Protein Maize (QPM) kernels contain twice the amounts of lysine and tryptophan compared to normal corn kernels. Although the opaque-2 (o2) mutation is the underlying cause of this beneficial change, other genes such as Aspartate kinase-2 (Ask2) affect the amino acid content in the endosperm to a lesser degree. To date, reports on the interaction between both loci are scarce and there are no high-throughput assays for the identification of the alleles of these genes. The objectives of this research were: 1) to study the interaction between the o2 and Ask2 genes with respect to the accumulation of amino acids in the endosperm in an F2 population, 2) to identify conserved SNPs into the o2 gene that can be used as markers, 3) to estimate the frequency of an SNP of Ask2 associated with the accumulation of lysine in the endosperm in CIMMYT germplasm, and 4) to develop high-throughput marker assays for these SNPs. The interaction study showed a preponderant effect of o2 on the accumulation of 11 amino acids (P ≤ 0.01). Ask2 appeared only to act with o2 to enhance marginally lysine, histidine and methionine levels in the double recessive homozygotes. Sequencing of amplicons at the o2 locus led to the identification of an SNP in exon 1 that discriminated all QPM (C) genotypes from non-QPM (T) genotypes. Validation of this SNP through KASP™ assays indicated that it was 92 % assertive in differentiating the o2 genotypes. In contrast, the frequency of the Ask2 SNP in CIMMYT QPM germplasm was low; however, an SSCP marker developed using this SNP detected five variants indicating that other unknown base changes may confer positive lysine-increasing responses. These markers could aid the marker-assisted selection of QPM cultivars.
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Journal
Revista Fitotecnia Mexicana
Journal volume
45
Journal issue
3
Article number
Place of Publication
Mexico
Publisher
Sociedad Mexicana de Fitogenetica
Related Datasets
CGIAR Initiatives
Initiative
Accelerated Breeding
Impact Area
Nutrition, health & food security
Action Area
Genetic Innovation
Donor or Funder
CGIAR Research Program on Maize
Harvest Plus
Harvest Plus