Genetic regulation of inflorescence development in chrysanthemum

Diversification of the Homeotic AP3 Clade MADS-Box Genes in Asteraceae Species Chrysanthemum morifolium L. and Helianthus annuus L

The structure and phylogeny of MADS-box genes HAM91 of sunflower (Helianthus annuus) and CDM115 of chrysanthemum (Chrysanthemum morifolium) were characterized. It is shown that these genes encode MADS-domain transcription factors, which are orthologs of TM6 (Solanum lycopersicum) and APETALA3 (Arabidopsis thaliana), respectively. We obtained two types of transgenic tobacco plants (Nicotiana tabacum) with constitutive expression of HAM91 and CDM115 genes. Both types of plants flowered later than the control plants and formed more flowers and seed pods. The weight of seeds of 35S::CDM115 plants was significantly lower than in the control and 35S::HAM91 plants, which may indicate to a change in the identity of ovules in 35S::CDM115.

Transcriptome analysis reveals genes related to floral development in chrysanthemum responsive to photoperiods

This research used the cDNA-AFLP technique to identify differentially expressed transcript-derived fragments (TDFs) in the apical tips of chrysanthemum induced by different photoperiods. Of the 3,152 TDFs screened by 64 primer recombinations, 861 were found to be differentially expressed, with 597 up-regulated and 264 down-regulated. We successfully cloned, sequenced, and analyzed the homologies of 57 TDFs. We found homologies for 37 of them in the NCBI: 31 displayed homology to genes with known functions, 3 to genes with unknown function, and 3 showed no matches. Functional analysis indicated that 34 TDFs participated in seven processes: transcription regulation, signal transduction, substance and energy metabolism, differentiation and development, protein degradation and synthesis, stress responses, and unclassified protein. Semi-quantitative RT-PCR analysis with selected transcripts of four genes related to floral development indicated that they all were expressed or up-regulated under short-day conditions. This was supported by analysis of cDNA-AFLP.

Identification and characterization of four chrysanthemum MADS-box genes, belonging to the APETALA1/FRUITFULL and SEPALLATA3 subfamilies

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.