Production of colored foliage phenotypes in Kalanchoe blossfeldiana by ectopic expression of R2R3 MYB genes

Ornamental plants with red, purple or violet foliage are often called “colored-leaf plants”. Colored foliage is generally resulted from accumulation of anthocyanins, which are synthesized through the flavonoid biosynthetic pathway, in leaf cells. R2R3-MYB, a member of the MYB transcription factor family, is known to activate the flavonoid biosynthetic pathway. In the present study, we examined genetic transformation of Kalanchoe blossfeldiana with R2R3-MYB genes from Tricyrtis sp. (TrMYB1) or Arabidopsis thaliana (PAP1) for producing novel colored-leaf plants. Totally nine and twelve independent transgenic plants have been obtained by transformation with TrMYB1 and PAP1, respectively. Transgenic plants could be classified into three types according to the leaf color phenotype: green leaves like those of the vector control plants (Type I), light red-purple leaves (Type II) and deep red-purple leaves (Type III). All three types were obtained by transformation with TrMYB1, whereas only Type I and Type II were obtained by transformation with PAP1. Type III transgenic plants also produced flowers with deeper red organs compared with the vector control plants. Spectrophotometric analysis showed that the total anthocyanin content in leaves of Type III transgenic plants was much higher than the vector control. Real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that TrMYB1 and PAP1 expression levels generally correlated with the degree of leaf color alteration. These results indicate that ectopic expression of the heterogeneous R2R3-MYB genes in K. blossfeldiana may activate the flavonoid biosynthetic pathway in leaves leading to anthocyanin accumulation and leaf color alteration.