Identification and quantification of expression levels of three FRUITFULL-like MADS-box genes from the orchid Dendrobium thyrsiflorum (Reichb. f.)

Orchids serve as useful model plants for the discovery and study of genes involved in novel processes in floral development because of their highly modified flowers. In this study three different FRUITFULL (FUL)-like MADS-box genes, DthyrFL1, -2, and -3 have been isolated from the orchid Dendrobium thyrsiflorum. Sequence alignment indicates that the entire sequence of exon 6 is missing in DthyrFL3 and that a frame shift could explain the missing FUL-like motif found in the sequence of both DthyrFL1 and -2. Phylogenetic analysis of the APETALA1/FRUITFULL lineage shows that FUL-like sequences from monocots all fall within one major clade and that subsequent gene duplication within this group is specific to monocots. At least two major duplication events have occurred: one before the split of the Poaceae and another within the Poaceae. Quantitative real-time RT-PCR analysis of the DthyrFL genes shows that they are expressed at different levels during inflorescence development but also transcribed in ovules and at very low levels in roots and leaves. These results suggest that the three FUL-like members are involved in floral development in D. thyrsiflorum. © 2005 Elsevier Ireland Ltd. All rights reserved.