Over-expression of an FT homolog from Prunus mume reduces juvenile phase and induces early flowering in rugosa rose

Abstract

Oil bearing rose (Rosa rugosa ‘Bao White’) is a perennial shrub and has a juvenile period of over 3 years before flowering. The Flowering Locus T (FT) gene from Prunus mume under the control of 35S promoter was transformed into this oil bearing rose. Eleven transgenic lines showed early flowering in vitro and the earliest three lines flowered within one month after the germination of transgenic somatic embryos. These extremely early flowering transgenic lines continued to flower after subculturing on the selection medium. The early-flowering PmFT transgenic lines also showed an increase in lignification of cells in stem, with radial files of xylem, phloem and cambium cells clearly differentiated. Quantitative real-time PCR indicated that FT gene was highly expressed in transgenic plants compared to control plants. Over-expression of FT gene also activated the transcription of the floral identity gene APETALA (AP1) and flowering time gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). These results showed that constitutive expression of PmFT can reduce juvenile phase and induce early and recurrent flowering in R. rugosa ‘Bao White’. This study also demonstrates the potential of using FT gene to significantly affect vegetative and reproductive growth of this important industrial fragrance oil bearing crop.