Biosynthesis of Salvia specialized metabolites and biotechnological approaches to increase their production

Aromatic Salvia species are particularly valuable for providing several bioactive compounds used as food additives, pigments, cosmetics, perfumes and fine chemicals. Within the Lamiaceae family, the Salvia genus, with more than 900 species, biosynthesizes a plethora of beneficial metabolites including terpenes, steroids and polyphenols. The whole plant can be considered a factory of bioactive compounds, but plant cell and tissue cultures are also an attractive sustainable alternative to cultivation. Salvia cell cultures can readily be initiated from different explants, including leaves, roots, stems, petioles, anthers and seedlings; however high metabolites accumulation in plant tissue and cell culture is a prerequisite for massive production of these bioactive compounds. In this chapter, the occurrence and tissue distribution of specialized metabolites in several Salvia species, especially flavonoids and diterpenoids, will be reviewed along with recent advances in the understanding of biosynthetic pathways as well as regulatory mechanisms leading to their biosynthesis. We will focus on the recent biotechnological approaches aimed at enhancing the final biomass and metabolite accumulation in Salvia cell and tissue cultures. Advances in metabolic engineering strategies will be also summarized, reporting relevant and successful results and potential pitfalls, in order to provide valuable perspectives for developing cell and tissue cultures as a reliable and standardized biomass platform for the extraction of Salvia bioactive metabolites.