Cloning and transcription analysis of an AGAMOUS- and SEEDSTICK ortholog in the orchid Dendrobium thyrsiflorum (Reichb. f.).

Studies have shown that several plant species possess AGAMOUS (AG) and SEEDSTICK (STK) orthologs. These genes are part of the so-called C- and D MADS-box gene lineages and play key roles in ovule development in Arabidopsis thaliana. We have cloned an AG- and STK ortholog in the orchid Dendrobium thyrsiflorum, named DthyrAG1 and DthyrAG2, respectively, and analyzed their expression patterns.

MADS-box gene evolution-structure and transcription patterns.

This study presents a phylogenetic analysis of 198 MADS-box genes based on 420 parsimony-informative characters. The analysis includes only MIKC genes; therefore several genes from gymnosperms and pteridophytes are excluded. The strict consensus tree identifies all major monophyletic groups known from earlier analyses, and all major monophyletic groups are further supported by a common gene structure in exons 1-6 and by conserved C-terminal motifs.

Genes from the APETALA3 and PISTILLATA lineages are expressed in developing vascular bundles of the tuberous rhizome, flowering stem and flower Primordia of Eranthis hyemalis.

In Arabidopsis thaliana expression of the B-class MADS-box genes APETALA3 (AP3) and PISTILLATA (PI) is confined to petals and stamens but in other plant species these genes are also transcribed in non-flower tissues; in Solanum tuberosum they are transcribed specifically in vascular bundles leading to petals and stamens. Transcription analysis of B-class genes in Eranthis hyemalis using reverse transcribed in situ PCR revealed that both AP3 and PI are expressed in developing vascular bundles in the tuberous rhizome, flowering stem and floral primordia. In addition, AP3 and PI transcripts are also found in stems and leaves.