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Schlagwörter:
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Zusammenfassung:
Background: Terpene rich leaves are a characteristic of Myrtaceae. There is significant qualitative variation in the
terpene profile of plants within a single species, which is observable as “chemotypes”. Understanding the molecular
basis of chemotypic variation will help explain how such variation is maintained in natural populations as well as
allowing focussed breeding for those terpenes sought by industry. The leaves of the medicinal tea tree, Melaleuca
alternifolia, are used to produce terpinen-4-ol rich tea tree oil, but there are six naturally occurring chemotypes;
three cardinal chemotypes (dominated by terpinen-4-ol, terpinolene and 1,8-cineole, respectively) and three
intermediates. It has been predicted that three distinct terpene synthases could be responsible for the maintenance
of chemotypic variation in this species.
Results: We isolated and characterised the most abundant terpene synthases (TPSs) from the three cardinal
chemotypes of M. alternifolia. Functional characterisation of these enzymes shows that they produce the dominant
compounds in the foliar terpene profile of all six chemotypes. Using RNA-Seq, we investigated the expression of
these and 24 additional putative terpene synthases in young leaves of all six chemotypes of M. alternifolia.
Conclusions: Despite contributing to the variation patterns observed, variation in gene expression of the three TPS
genes is not enough to explain all variation for the maintenance of chemotypes. Other candidate terpene synthases
as well as other levels of regulation must also be involved. The results of this study provide novel insights into the
complexity of terpene biosynthesis in natural populations of a non-model organism.
