Activation tagging in Salvia miltiorrhiza can cause increased leaf size and accumulation of Tanshinone I and IIA in its roots

Background: Salvia miltiorrhiza Bunge (Danshen), an important herb in traditional Chinese medicine, is commonly used for treatment of cardiovascular diseases. One of the major bioactive constituents of Danshen, diterpenoid tanshinone, has been proved with pharmacological properties and have the potential to be a new drug candidate against various diseases. In our previous study, we have established an activation tagging mutagenesis (ATM) population of callus lines of S. miltiorrhiza Bunge by Agrobacteriummediated transformation. Results: In the present study, we have identified ATM transgenic Salvia plant (SH41) with different leaf morphology and more tanshinones in its roots. The transgenic background of SH41 was identified by PCR (using hptII primers) and Southern blots. PCR analysis showed a single band of hptII gene and Southern blot analysis showed single insertion in SH41. External appearance of ATM transgenic SH41 was observed with broader leaves comparing to non-transformed plants. More healthy trichomes as well as bigger and wobbly guard cells and stomata were observed in SH41 by scanning electron microscopy (SEM). Quantitative analysis of active compounds in SH41 roots revealed a significant increase in tanshinone I (3.7 fold) and tanshinone IIA (2 fold) contents as compared to the wild plant. Conclusions: We have generated an activation tagged transgenic Salvia plant (SH41) with different leaf morphology and high diterpenes content in its roots. The increased amount of tanshinones in SH41 will definitely offer a route for maximizing the benefits of this plant in traditional Chinese herbal medicines. The present report may also facilitate the application of ATM for genetic manipulation of other medicinal crops and subsequent improved metabolite contents.