Influence of culture media and fungal extracts on essential oils composition and on terpene synthase gene expression in Thymus caespititius

Thymus caespititius Brot. is an Iberian endemic species, whose essential oils possess high diversity and some of them could be used in pharmaceutical and food industries. The effect of culture media composition and fungal extracts on essential oils composition and on the expression of terpene synthase (TPS) genes was evaluated in T. caespititius shoots cultures. Nutrient composition influenced quantitatively the essential oils content. A decrease in the acetate compounds in the essential oils was observed in SH medium as compared with MS. The TPS transcripts accumulation was higher in all genotypes grown in SH, except in sabinene/carvacrol (SC) genotype. B. cinerea extracts highly induced TPS gene expression in the first hours after treatment in SC genotype, while in carvacrol/thymol (CT) only a slight increase was observed. TPS down-regulation observed during the next time points could result from reallocation of energy resources to plants’ vital functions. Fungal extracts did not affect qualitatively and quantitatively the CT essential oils, however in SC, the sabinene relative content decreased and this was inversely related to the increase of two antifungal compounds, carvacrol and thymol, in the oil. T. caespititius in vitro cultures revealed to be a good system for terpene metabolism study.