Sesquiterpene Synthases of Zanthoxylum ailanthoides: Sources of Unique Aromas of a Folklore Plant in Taiwan

Abstract

Zanthoxylum ailanthoides is a traditional spice crop in Taiwan with unique smells and tastes that differ between prickly (young) and nonprickly (mature) leaves. Different volatile terpenes between prickly young and nonprickly mature leaves were identified and considered to be one of the sources of their aromas. A transcriptome database was established to explore the biosynthesis of these compounds, and candidate terpene synthase genes were identified. The functions of these synthases were investigated using recombinant protein reactions in both purification and coexpression assays. ZaTPS1, ZaTPS2, and ZaTPS3 are germacrene D synthases, with different amino acid sequences. The main products of ZaTPS4 are trans-α-bergamotene and (E)-β-farnesene, whereas ZaTPS5 forms multiple products, and ZaTPS6 produces β-caryophyllene. ZaTPS7 forms monoterpene (E)-β-ocimene and sesquiterpene (E,E)-α-farnesene. Reverse transcription PCR of ZaTPS gene expression in young and mature leaves revealed that ZaTPS1 was responsible for the mellow aroma in mature leaves. The expression of ZaTPS6 suggested that it plays a role in the background aromas of both types of leaves. Our findings deepened the understanding of the volatile compounds of Z. ailanthoides and revealed the source of its unique aromas by clarifying the biosynthesis of these compounds.

Quick shift in volatile attraction between the third and fifth instar larvae of Endoclita signifier

“…8 For example, volatile profiles of Fagus grandifolia leaves were reported to change significantly throughout the growing season 4 and likewise the terpene profiles between young and mature leaves of Zanthoxylum ailanthoides. 9 On the other hand, insects have developed an olfactory system with remarkable sensitivity, specificity, and dynamics. It is largely accepted that larval experiences influence host-plant preference to adults.…”

“…On one hand, within a plant, the composition of the volatile emission can differ among organs and may vary with the circadian rhythm, the plant's age and phenological state 8 . For example, volatile profiles of Fagus grandifolia leaves were reported to change significantly throughout the growing season 4 and likewise the terpene profiles between young and mature leaves of Zanthoxylum ailanthoides 9 . On the other hand, insects have developed an olfactory system with remarkable sensitivity, specificity, and dynamics.…”