Ectopic expression of the Osmyb4 rice gene enhances synthesis of hydroxycinnamic acid derivatives in tobacco and clary sage.

In this work, we report the ectopic expression of the Osmyb4 rice gene, encoding the Myb4 transcription factor, in Nicotiana tabacum and Salvia sclarea. Transcriptional analysis of T2 homozygous tobacco plants overexpressing Osmyb4 revealed that Myb4 activated the transcription of several genes of the phenylpropanoid pathway such as PAL, C4H, 4CL1, 4CL2 (encoding phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, 4-coumarate: CoA ligase1, 4-coumarate: CoA ligase2). Moreover, the Myb4 increased expression of HQT encoding hydroxycinnamoyl-CoA: quinate transferase, which specifically triggers the accumulation of chlorogenic acid (CGA). In addition, increased acccumulation of rosmarinic acid (RA) was found in transgenic plants of both species. These results open the possibility of using the Osmyb4 gene to increase the production of specific bioactive hydroxycinnamates.