Peach is not an important fruit crop of the temperate zone, but also serves as a source of valuable ornamental plants due to the beauty of flowers. The peach double-flower variant with higher ornamental value is characterized by supernumerary petals, but the mechanism underlying its development remains elusive.   

Supervised by Prof. HAN Yuepeng from the Wuhan Botanical Garden of the Chinese Academy of Sciences, CAI Yaming investigated ABCE model genes (genes that control flower organ formation) in the peach genome and their potential roles in controlling double flower formation. Together they revealed the mechanisms of the double-flower formation in peach.  

They identified nine ABCE model genes including eight MADS-box genes (genes which encoding a family of transcription factors that have fundamental roles in controlling the development of plants, animals, and fungi) and one AP2/EREBP (AP2/ethylene-responsive element-binding protein) gene from peach reference genome sequences. All the nine ABCE model genes were localized in the nucleus by analyzing subcellular localization in tobacco leaves.

Moreover, PpAP1, PpAP3, PpSEP3 and PpPI were all highly expressed in petals or petaloid organs, and their expression in the petal differentiation stage showed a difference between single and double flowers. Ectopic overexpression of PpPI in Arabidopsis increased petal number, and transgenic lines overexpressing PpAP1 caused early flowering. However, overexpressing either PpAP3 or PpSEP3 in Arabidopsis was morphologically indistinguishable from wild type plants. Results reveal that PpPI might be the key regulator for double flower formation in peach.   

Interestingly, the researchers found single flower varieties also contained petaloid stamens, such as 'Qianqu'. And PpPI was the most highly expressed in the petals and petaloid stamens of 'Qianqu'. Therefore, double flower is likely to have developed from single flower through conversion of stamens to petals, which could be due to an increase in the expression of PpPI in peach.    

Results have been published in Physiologia Plantarum entitled "The MADS-box gene PpPI is a key regulator of the double-flower trait in peach."

 Comparison of flower morphology between the single flower, 'Fenshou' ( 'FS') and the double flower, 'Beijing 2-7' ( 'BJ'). (Image by CAI Yaming)