MADS-box genes play important roles in the regulation of floral organ development. In this gene family, AGAMOUS genes are responsible for stamen and carpel development. In the double-flowered form of Amaryllis, compared to its wild type, the stamen number is reduced to three, there is no pistil, and, in contrast, tepal numbers have increased. In this investigation, we examined the AGAMOUS (AG) gene function in these alterations. Therefore, we isolated one AGAMOUS coding sequence named AmAG. Then, the expression level of this gene in the wild form and double-flowered Amaryllis was evaluated using quantitative real-time PCR. The phylogenetic results showed that the partial AmAG gene has high homology with the sequences of AGAMOUS ortholog genes in the Amaryllidaceae family and plants close to this family. Also, there were no differences in the sequence of partial AmAG genes in wild and double-flowered forms. Real-time PCR revealed that, in wild form, AmAG gene expression was low in the first to third whorl and high only in the fourth whorl. While in double flowered form, AmAG gene expression in four whorls was low. The lower expression of AmAG in the fourth whorl of double-flowered form had caused such morphological alterations, the reasons for which should be determined in other experiments.

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