Abstract
BackgroundTerpenoids are abundant in the foliage of Eucalyptus, providing the characteristic smell as well as being valuable economically and influencing ecological interactions. Quantitative and qualitative inter- and intra- specific variation of terpenes is common in eucalypts.ResultsThe genome sequences of Eucalyptus grandis and E. globulus were mined for terpene synthase genes (TPS) and compared to other plant species. We investigated the relative expression of TPS in seven plant tissues and functionally characterized five TPS genes from E. grandis. Compared to other sequenced plant genomes, Eucalyptus grandis has the largest number of putative functional TPS genes of any sequenced plant. We discovered 113 and 106 putative functional TPS genes in E. grandis and E. globulus, respectively. All but one TPS from E. grandis were expressed in at least one of seven plant tissues examined. Genomic clusters of up to 20 genes were identified. Many TPS are expressed in tissues other than leaves which invites a re-evaluation of the function of terpenes in Eucalyptus.ConclusionsOur data indicate that terpenes in Eucalyptus may play a wider role in biotic and abiotic interactions than previously thought. Tissue specific expression is common and the possibility of stress induction needs further investigation. Phylogenetic comparison of the two investigated Eucalyptus species gives insight about recent evolution of different clades within the TPS gene family. While the majority of TPS genes occur in orthologous pairs some clades show evidence of recent gene duplication, as well as loss of function.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1598-x) contains supplementary material, which is available to authorized users.
Highlights
Terpenoids are abundant in the foliage of Eucalyptus, providing the characteristic smell as well as being valuable economically and influencing ecological interactions
We describe the Eucalyptus grandis terpene synthase genes (TPS) gene family from the recently sequenced reference genome of E. grandis (V1.1 annotation, www.phytozome.net) [23] and make comparisons with a second species of Eucalyptus that has been sequenced (E. globulus) to understand how this gene family is arranged and how it has evolved over the relatively short time that these two species separated (Thornhill, Külheim and Crisp unpublished) and how it has contributed to the success of the genus Eucalyptus across its native and introduced range
Discovery of putative TPS genes from the E. grandis genome We identified 172 loci in the Eucalyptus grandis genome with a high sequence similarity to known terpene synthase genes from other species
Summary
Terpenoids are abundant in the foliage of Eucalyptus, providing the characteristic smell as well as being valuable economically and influencing ecological interactions. Eucalyptus dominates Australian forests and woodlands and is truly the “essence” of Australia as well as being the dominant hardwood plantation tree in the world. Foliar terpenes give eucalypts their characteristic odour, they are industrially important and mediate many ecological interactions. Eucalyptus terpenes act to mediate ecological interactions including deterrents to insect herbivory [1,2], attractants [3] and repellents to vertebrate herbivores [4], cues to other toxic. No terpenes are found exclusively in eucalypts, striking variation can be observed in the foliar terpene profile within a single species [13] or even within individual branches of a single tree [14]. We show that this variation is built on the largest family of terpene synthase genes of any plant yet sequenced
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