CHRYSANTHEMUM MODIFICATION VIA ECTOPIC EXPRESSION OF SUNFLOWER MADS-BOX GENE HAM59

Flower and plant shape are important characteristics in ornamental plants. A possible strategy to modify flower shape is genetic manipulation of regulators of floral organ identity. Plant MADS-box transcription factors play key roles in this process. C-function MADS-box genes specify stamen and carpel development, the repression of A-class genes, and the floral meristem determinacy. This process is generally conserved. Previously, we have identified AGAMOUS-like cDNAs from Chrysanthemum (CDM37) and Helianthus (HAM45 and HAM59). In this work, Chrysanthemum flower shape was analysed after ectopic expression of HAM59. Twelve transgenic lines were isolated showing reduced male fertility. Two transgenic lines had modified floret structures. In disk florets, stamens were transformed into petal-like structures, resembling the double flower phenotype in Arabidopsis agamous mutants. In addition, ray floret petals were shorter than control, and ligule tips were divided. However, there were no homeotic changes of floral organs in ray florets. In conclusion we show that ectopic expression of sunflower HAM59 gene modifies androecium to corolla-like tissues and leads to male-sterility.