Molecular Analysis Of Hormone-regulated Inflorescence Development In Arabidopsis

Plant hormones play important roles in the regulation of flower development. To study hormone-regulated inflorescence development, we established two different in vitro regeneration systems of Arabidopsis inflorescences in the presence of cytokinin and auxin. The inflorescence stems of wild type Arabidopsis (Ecotype Wassilewskija) were excised into 2~3 mm lengths as explants when the first flowers of the plants were at anthesis. In the first regeneration system, media containing a combination of thidiazuron (TDZ) and 2,4-Dichlorophenoxyacetic acid (2,4-D) were used to induce callus formation. Higher frequencies of calli formation were obtained. After transferring the calli to media containing a combination of zeatin and indole-3-acetic acid (IAA), the inflorescences were induced from the calli. However, in the second regeneration system, calli and in vitro inflorescences were induced in the media containing the same combination of zeatin and IAA. Two types of inflorescences were observed in this study. The first-type, which have cauline leaves, were similar to those in plants, whereas, the second-type showed some abnormal morphology and had no cauline leaves. In the first system, most flowers of the regenerated inflorescences had four whorls of floral organs, but some of them lacking a few organs, such as petals or stamens, which led to the sterility of the regenerated inflorescences. However, most of the in vitro inflorescences were fertile and mature seeds could be obtained in the second system.Semiquantitative RT-PCR was performed to determine the patterns of TFL1 (TERMINAL FLOWER1) and TFL2 expression during the regeneration of inflorescence in the first system. The results indicated that TFL1 expression was induced during regeneration of inflorescence while TFL2 showed constitutive expression pattern. Further, we examined the expression of beta-glucuronidase (GUS) gene driven by the TFL1 promoter during the...