Glandular secretory trichomes formation mechanism study on synthesis and storage of terpenoids in lavender

Abstract Background: Lavender belongs to the family Lamiaceae and is an aromatic plant that is widely grown as an ornamental plant. The chemical components of lavender are characterized by the presence of monoterpenoids and sesquiterpenoidsand other irregular types. These main compounds are primarily synthesized and stored in an epidermal secretory structure, glandular secretory trichomes (GSTs). Results: Volatile organic compounds (VOCs) are responsible for the aroma characteristics of plant oil that drive consumer preference. It is usually regarded as a characteristic character in the classification of aromatic plants. Interestingly, VOCs are synthesized and stored in GSTs. In this study, we measured the VOCs of four lavenders by HS-SPME-GC-MS. Among them, 66 volatile organic compounds were identified, flowers were the main site of accumulation of VOCs and its prominent components were linalyl acetate and linalool. In Lamiaceae, GSTs usually include peltate glandular trichomes (PGTs) and capitate glandular trichomes (CGTs), like Perilla frutescens , peppermint, Ocimum basilicum , thyme, oregano, etc. But there were no reports about GSTs in lavender until now. We also examined the developmental processes of PGTs, it included the head and the stalk region, the head cells have a secretory, VOCs are produced by these secretory cells. Based on a reference genome from ‘Jingxun 2’, several genes related to GSTs belonged to R2R3-MYB subfamily had been identified. These results will give a directive sense for GSTs engineering and molecular breeding of lavender for targeting VOCs. Conclusions: In this study, we used HS-SPME-GC/MS to identify VOCs of these lavenders. We analyzed the formation of GSTs in lavender and compared quantity and diameter size of four lavenders. In the meanwhile, we found four candidate genes belonging to R2R3-MYB family.