Functional characterization and transient expression manipulation of a new sesquiterpene synthase involved in β-caryophyllene accumulation in Ocimum

• A new β-caryophyllene synthase is isolated from Ocimum kilimandscharicum (OkBCS).
• OkBCS encodes 542 amino acids with mass of 63.6 kDa and pI of 5.66.
• Enzyme coverts FPP into β-caryophyllene (94%) and α-humulene (6%).
• OkBCS expression correlates with β-caryophyllene levels in tissues of 5 Ocimum spp.
• Transient expression of OkBCS corroborates its role in β-caryophyllene accumulation.

The genus Ocimum has a unique blend of diverse secondary metabolites, with major proportion of terpenoids including mono- and sesquiterpenes. Although, β-Caryophyllene, bicyclic sesquiterpene, is one of the major terpene found in Ocimum species and known to possess several biological activities, not much is known about its biosynthesis in Ocimum. Here, we describe isolation and characterization of β-caryophyllene synthase gene from Ocimum kilimandscharicum Gürke (OkBCS- GenBank accession no. KP226502). The open reading frame of 1629 bp encoded a protein of 542 amino acids with molecular mass of 63.6 kDa and pI value of 5.66. The deduced amino acid sequence revealed 50–70% similarity with known sesquiterpene synthases from angiosperms. Recombinant OkBCS converted farnesyl diphosphate to β-caryophyllene as a major product (94%) and 6% α-humulene. Expression variation of OkBCS well corroborated with β-caryophyllene levels in different tissues from five Ocimum species. OkBCS transcript revealed higher expression in leaves and flowers. Further, agro-infiltration based transient expression manipulation with OkBCS over-expression and silencing confirmed its role in β-caryophyllene biosynthesis. These findings may potentially be further utilized to improve plant defense against insect pests.

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