| Title: | Monoterpene synthases responsible for the terpene profile of anther glands in Eucalyptus polybractea R.T. Baker (Myrtaceae) |
| Author(s): | Goodger JQD; Sargent D; Humphries J; Woodrow IE; |
| Address: | "School of BioSciences, The University of Melbourne, Parkville, Victoria 3010, Australia. Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW 2753, Australia. School of Ecosystem and Forest Sciences, The University of Melbourne, Victoria 3010, Australia" |
| ISSN/ISBN: | 1758-4469 (Electronic) 0829-318X (Linking) |
| Abstract: | "Research on terpene biosynthesis in the genus Eucalyptus (Myrtaceae) is poorly developed, but recently large numbers of terpene synthase (TPS) genes have been identified. Few of these have been characterized or their expression localized to specific tissues. A prime candidate for detailed examination of TPS gene expression is the bisexual eucalypt flower-composed of male and female reproductive organs, and vegetative tissues that may express different TPS genes. We aimed to characterize and compare the terpene profile and TPS genes expressed in anthers and gynoecia in the high oil-yielding Eucalyptus polybractea R.T. Baker. We hypothesized that gynoecia will produce greater amounts of defensive terpenes, whereas anthers will have a terpene profile that is biased towards a role in pollination. Microscopy of isolated anthers showed them to possess a single, prominent oil gland. Chemical analysis of whole floral structures at different stages of development showed total oil per unit dry mass increased as flower buds expanded, with highest concentrations in mature flower buds just prior to flower opening. The oil profile of gynoecia was dominated by the monoterpene 1,8-cineole, whereas that of isolated anthers were enriched with the monoterpene alpha-pinene. Through transcriptomic analysis and recombinant protein expression, we were able to identify monoterpene synthases responsible for the different profiles. Synthases for alpha-pinene and 1,8-cineole were expressed in each tissue type, but the relative expression of the former was higher in anthers. Sequence comparison and site-directed mutagenesis of the alpha-pinene synthase allowed us to identify amino acids that influence the alpha-pinene to beta-pinene ratio of the product profile. We suggest the terpene constituents of anthers may have multiple roles including attracting pollinators through emission of volatile alpha-pinene, deterrence of palynivores through emission of volatile 1,8-cineole and adhesion of pollen to pollinators via the release of sticky alpha-pinene onto the anther surface" |
| Keywords: | "*Alkyl and Aryl Transferases/genetics *Eucalyptus/genetics Flowers/genetics Monoterpenes *Myrtaceae/genetics Terpenes 1, 8-cineole cineole cassette flower pinene secretory cavity terpenoid;" |
| Notes: | "MedlineGoodger, Jason Q D Sargent, Demi Humphries, John Woodrow, Ian E eng Research Support, Non-U.S. Gov't Canada 2020/11/22 Tree Physiol. 2021 May 14; 41(5):849-864. doi: 10.1093/treephys/tpaa161" |
