Free Amino Acids in Maize (Zea mays L.) Anthers During Microsporogenesis

The objective of this work was to identify and quantify the free amino acids in the anther of the hybrid maize H-34 and the traditional cultivar Zac.58-VO during microsporogenesis. Anthers were studied in three stages of their development: (I) differentiation, (II) mid-uninucleate meiotic stage, and (III) at anthesis of plants growing in the field. Amino acids were chemically modified with o-phthaldialdehyde and quantified by HPLC. Anthers of the traditional cv. Zac.58-VO had a low concentration of free amino acids, especially at stage I. This cultivar reached the highest amino acid concentration at stage II (2 502 nmols/100 mg of fresh tissue) with alanine, asparagine and glutamate occurring as the most abundant amino acids (70 % of the total). In contrast, the amino acid content in the anthers of the hybrid H-34 dramatically increased with anther development, from 1 278 nmols/100 mg in stage I to 5 799 in the stage III. Among the 18 amino acids identified some of the most abundant were aspartate, glutamate, asparagine and glutamine, and γ-aminobutyric acid was found only in this cultivar (H-34). In both cultivars, alanine, asparagine, aspartate, phenylalanine and valine presented high positive correlation with other amino acids. In the hybrid, another nine amino acids increased to 105 the total number of significant correlations between pairs of amino acids, in contrast with only 35 in the traditional cultivar. The results support the hypothesis that the content of amino acids in the anthers of maize varies with the stage of anther development and with the cultivar.