Abstract:

The apple α-farnesene synthase gene（MdAFS）was cloned by combination of the homologous clone and PCR technology from apple（Malus × domestica‘White Winter Pearmain’）. By using chloroplast transit peptide（pla）of the AtCor15A gene from Arabidopsis thaliana，we targeted MdAFS to the chloroplast of Arabidopsis to generate pla + MdAFS transgenic lines. Transgenic Arabidopsis was generated by Agrobacterium-mediated genetic transformation. The subcellular localization of the pla-MdAFS-GFP fusion fluorescent protein revealed that the MdAFS protein was localized in chloroplast. The quantification of photosynthesis-related isoprenoid metabolites in all plants at the rosette and flowering stages showed that chlorophyll a，chlorophyll b，total chlorophyll，and carotenoid were higher in the transgenic lines as compared to wild-type control. The expressions of terpenoid biosynthetic genes were investigated in different development stages by qRT-PCR. Especially，at the flowering stage，the expression of several terpenoid biosynthetic genes significantly increased in the transgenic lines. Gas chromatography mass spectrometry（GC–MS）analysis of volatile extracts from the transgenic plants revealed the biosynthesis of several novel sesquiterpenes，including (E,E)-α-farnesene. These results indicated that overexpressing MdAFS in chloroplast of Arabidopsis could significantly affect the reorientation of terpene metabolic pathway，and increase the transgenic plant emitting terpene volatiles.

Key words: apple, Arabidopsis thaliana, AFS, chloroplast localization, terpenoid metabolism；terpene volatile