Four full-length MADS-box cDNAs from chrysanthemum, designated Chrysanthemum Dendrathema grandiflorum MADS (CDM) 8, CDM41, CDM111, and CDM44, have been isolated and further functionally characterized. Protein sequence alignment and expression patterns of the corresponding genes suggest that CDM8 and CDM41 belong to the FRUITFULL (FUL) clade, CDM111 is a member of the APETALA1 (AP1) subfamily, and CDM44 is a member of the SEPALLATA3 (SEP3) subfamily of MADS-box transcription factors. Overexpression of CDM111 in Arabidopsis plants resulted in an aberrant phenotype that is reminiscent of the phenotype obtained by ectopic expression of the AP1 gene. In addition, CDM111 was able to partially complement the ap1-1 mutant from Arabidopsis, illustrating that CDM111 is the functional equivalent to AP1. Yeast two-and three-hybrid studies were performed to investigate the potential protein interactions and complexes in which these chrysanthemum MADS-box proteins are involved. Based on these studies, we conclude that CDM44 is most likely the SEP3 functional equivalent, because the CDM44 protein interacts with CDM proteins of the AP1/FUL and AG subfamilies, and as a higher order complex with the heterodimer between the presumed B-type CDM proteins.

Chrysanthemum is one of the most important commercial cut flowers in the world. Early-flowering cultivars are required to produce quality chrysanthemum flowers with a lower cost of production. To shorten the vegetative growth phase of chrysanthemum, three AP1-like genes from Asteraceae were constitutively overexpressed in 80 independent transgenic chrysanthemum lines. All lines were characterized by PCR and RT-PCR and demonstrated that overexpression of compositae AP1-homologs in transgenic chrysanthemum under long-day conditions had no effect on plant development compared to non-transgenic controls. Conversely, under short-day conditions, transgenic plants commenced bud initiation 2 wk earlier than non-transgenic chrysanthemum plants. Subsequently, transgenic chrysanthemum flowers showed color earlier and resulted in full opening of inflorescences 3 wk prior to non-transgenic control plants. These results open new possibilities for genetic improvement and breeding of chrysanthemum cultivars.

Monotropa hypopitys is a mycoheterotrophic, nonphotosynthetic plant acquiring nutrients from the roots of autotrophic trees through mycorrhizal symbiosis, and, similar to other extant plants, forming asymmetrical lateral organs during development. The members of the YABBY family of transcription factors are important players in the establishment of leaf and leaf-like organ polarity in plants. This is the first report on the identification of YABBY genes in a mycoheterotrophic plant devoid of aboveground vegetative organs. Seven M. hypopitys YABBY members were identified and classified into four clades. By structural analysis of putative encoded proteins, we confirmed the presence of YABBY-defining conserved domains and identified novel clade-specific motifs. Transcriptomic and qRT-PCR analyses of different tissues revealed MhyYABBY transcriptional patterns, which were similar to those of orthologous YABBY genes from other angiosperms. These data should contribute to the understanding of the role of the YABBY genes in the regulation of developmental and physiological processes in achlorophyllous leafless plants.