840 research outputs found

    Differences in gene expression within a striking phenotypic mosaic Eucalyptus tree that varies in susceptibility to herbivory

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    BACKGROUND Long-lived trees can accumulate mutations throughout their lifetimes that may influence biotic and abiotic interactions. For example, some Eucalyptus trees display marked variation in herbivore defence within a single canopy. These "mosaic" trees support foliage with distinct chemotypes which are differentially favoured by insect and vertebrate herbivores, resulting in susceptible and resistant branches within a single canopy. These mosaic trees provide a unique opportunity to explore the biosynthesis and genetic regulation of chemical defences in the foliage. The biosynthesis of the principal defence compounds, terpenoid-dominated essential oils, is well understood. However, the regulation of the genes involved and thus the control of phenotypic variation within a single tree canopy remains a mystery. RESULTS We sequenced the transcriptomes of the leaves of the two different chemotypes of a chemically mosaic Eucalyptus melliodora tree using 454 pyrosequencing technology. We used gene set enrichment analysis to identify differentially expressed transcripts and found the proportion of differentially expressed genes in the resistant and susceptible foliage similar to the transcript difference between functionally distinct tissues of the same organism, for example roots and leaves. We also investigated sequence differences in the form of single nucleotide polymorphisms and found 10 nucleotides that were different between the two branches. These are likely true SNPs and several occur in regulatory genes. CONCLUSION We found three lines of evidence that suggest changes to a 'master switch' can result in large scale phenotypic changes: 1. We found differential expression of terpene biosynthetic genes between the two chemotypes that could contribute to chemical variation within this plant. 2. We identified many genes that are differentially expressed between the two chemotypes, including some unique genes in each branch. These genes are involved in a variety of processes within the plant and many could contribute to the regulation of secondary metabolism, thus contributing to the chemical variation. 3. We identified 10 SNPs, some of which occur in regulatory genes that could influence secondary metabolism and thus contribute to chemical variation. Whilst this research is inherently limited by sample size, the patterns we describe could be indicative of other plant genetic mosaics.This work was supported by a Discovery grant from the Australian Research Council to WJF (DP0877063)

    The influence of leg-to-body ratio, arm-to-body ratio and intra-limb ratio on male human attractiveness.

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    Human mate choice is influenced by limb proportions. Previous work has focused on leg-to-body ratio (LBR) as a determinant of male attractiveness and found a preference for limbs that are close to, or slightly above, the average. We investigated the influence of two other key aspects of limb morphology: arm-to-body ratio (ABR) and intra-limb ratio (IR). In three studies of heterosexual women from the USA, we tested the attractiveness of male physiques that varied in LBR, ABR and IR, using figures that ranged from -3 to +3 standard deviations from the population mean. We replicated previous work by finding that the optimally attractive LBR is approximately 0.5 standard deviations above the baseline. We also found a weak effect of IR, with evidence of a weak preference for the baseline proportions. In contrast, there was no effect of ABR on attractiveness, and no interactions between the effects of LBR, ABR and IR. Our results indicate that ABR is not an important determinant of human mate choice for this population, and that IR may exert some influence but that this is much smaller than the effects of LBR. We discuss possible reasons for these results, including the limited variability in upper limb proportions and the potentially weak fitness-signal provided by this aspect of morphology

    The Yield of Essential Oils in Melaleuca alternifolia (Myrtaceae) Is Regulated through Transcript Abundance of Genes in the MEP Pathway

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    Medicinal tea tree (Melaleuca alternifolia) leaves contain large amounts of an essential oil, dominated by monoterpenes. Several enzymes of the chloroplastic methylerythritol phosphate (MEP) pathway are hypothesised to act as bottlenecks to the production of monoterpenes. We investigated, whether transcript abundance of genes encoding for enzymes of the MEP pathway were correlated with foliar terpenes in M. alternifolia using a population of 48 individuals that ranged in their oil concentration from 39 -122 mg x g DM(-1). Our study shows that most genes in the MEP pathway are co-regulated and that the expression of multiple genes within the MEP pathway is correlated with oil yield. Using multiple regression analysis, variation in expression of MEP pathway genes explained 87% of variation in foliar monoterpene concentrations. The data also suggest that sesquiterpenes in M. alternifolia are synthesised, at least in part, from isopentenyl pyrophosphate originating from the plastid via the MEP pathway.The work was funded by an Australian Research Council Linkage grant to W.J.F. (LP110100184) with the active partnership of the Australian Tea Tree Industry Association (ATTIA) and a supplementary grant from the Rural Industries Research and Development Corporation. The funders had no role is study design, data collection and analysis, decision to publish, or preparation of the manuscript

    Accuracy of Genomic Prediction for Foliar Terpene Traits in Eucalyptus polybractea

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    Unlike agricultural crops, most forest species have not had millennia of improvement through phenotypic selection, but can contribute energy and material resources and possibly help alleviate climate change. Yield gains similar to those achieved in agricultural crops over millennia could be made in forestry species with the use of genomic methods in a much shorter time frame. Here we compare various methods of genomic prediction for eight traits related to foliar terpene yield in Eucalyptus polybractea, a tree grown predominantly for the production of Eucalyptus oil. The genomic markers used in this study are derived from shallow whole genome sequencing of a population of 480 trees. We compare the traditional pedigree-based additive best linear unbiased predictors (ABLUP), genomic BLUP (GBLUP), BayesB genomic prediction model, and a form of GBLUP based on weighting markers according to their influence on traits (BLUP|GA). Predictive ability is assessed under varying marker densities of 10,000, 100,000 and 500,000 SNPs. Our results show that BayesB and BLUP|GA perform best across the eight traits. Predictive ability was higher for individual terpene traits, such as foliar α-pinene and 1,8-cineole concentration (0.59 and 0.73, respectively), than aggregate traits such as total foliar oil concentration (0.38). This is likely a function of the trait architecture and markers used. BLUP|GA was the best model for the two biomass related traits, height and 1 year change in height (0.25 and 0.19, respectively). Predictive ability increased with marker density for most traits, but with diminishing returns. The results of this study are a solid foundation for yield improvement of essential oil producing eucalypts. New markets such as biopolymers and terpene-derived biofuels could benefit from rapid yield increases in undomesticated oil-producing species.Funding for this project was provided by the Australian Research Council Linkage Program (LP110100184) toWJF, the Rural Industries Research and Development Corporation (RIRDC), Australia. Support was also provided by the Center for BioEnergy Innovation (CBI), a U.S DOE Bioenergy Research Center supported by the DOE office of science

    Male-biased predation and its effect on paternity skew and life history in a population of common brushtail possums (Trichosurus vulpecula)

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    Differences in predation risk may exert strong selective pressures on life history strategies of populations. We investigated the potential for predation to shape male mating strategies in an arboreal folivore, the common brushtail possum (Trichosurus vulpecula Kerr). We predicted that possums in a tropical population exposed to high natural levels of predation would grow faster and reproduce earlier compared to those in temperate populations with lower predation. We trapped a population of possums in eucalypt woodland in northern Australia each month to measure life history traits and used microsatellites to genotype all individuals and assign paternity to all offspring. We observed very high levels of male-biased predation, with almost 60% of marked male possums being eaten by pythons, presumably as a result of their greater mobility due to mate-searching. Male reproductive success was also highly skewed, with younger, larger males fathering significantly more offspring. This result contrasts with previous studies of temperate populations experiencing low levels of predation, where older males were larger and the most reproductively successful. Our results suggest that in populations exposed to high levels of predation, male possums invest in increased growth earlier in life, in order to maximise their mating potential. This strategy is feasible because predation limits competition from older males and means that delaying reproduction carries a risk of failing to reproduce at all. Our results show that life histories are variable traits that can match regional predation environments in mammal species with widespread distributions.This work was supported by the Australian Research Council http://www.arc.gov.au/ Grant number DP0449621 to CNJ, DP0449544 to WJF. JLD was supported by an Australian National University Graduate School Scholarship

    Comparative SNP diversity among four Eucalyptus species for genes from secondary metabolite biosynthetic pathways

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    <p>Abstract</p> <p>Background</p> <p>There is little information about the DNA sequence variation within and between closely related plant species. The combination of re-sequencing technologies, large-scale DNA pools and availability of reference gene sequences allowed the extensive characterisation of single nucleotide polymorphisms (SNPs) in genes of four biosynthetic pathways leading to the formation of ecologically relevant secondary metabolites in <it>Eucalyptus</it>. With this approach the occurrence and patterns of SNP variation for a set of genes can be compared across different species from the same genus.</p> <p>Results</p> <p>In a single GS-FLX run, we sequenced over 103 Mbp and assembled them to approximately 50 kbp of reference sequences. An average sequencing depth of 315 reads per nucleotide site was achieved for all four eucalypt species, <it>Eucalyptus globulus</it>, <it>E. nitens</it>, <it>E. camaldulensis </it>and <it>E. loxophleba</it>. We sequenced 23 genes from 1,764 individuals and discovered 8,631 SNPs across the species, with about 1.5 times as many SNPs per kbp in the introns compared to exons. The exons of the two closely related species (<it>E. globulus </it>and <it>E. nitens</it>) had similar numbers of SNPs at synonymous and non-synonymous sites. These species also had similar levels of SNP diversity, whereas <it>E. camaldulensis </it>and <it>E. loxophleba </it>had much higher SNP diversity. Neither the pathway nor the position in the pathway influenced gene diversity. The four species share between 20 and 43% of the SNPs in these genes.</p> <p>Conclusion</p> <p>By using conservative statistical detection methods, we were confident about the validity of each SNP. With numerous individuals sampled over the geographical range of each species, we discovered one SNP in every 33 bp for <it>E. nitens </it>and one in every 31 bp in <it>E. globulus</it>. In contrast, the more distantly related species contained more SNPs: one in every 16 bp for <it>E. camaldulensis </it>and one in 17 bp for <it>E. loxophleba</it>, which is, to the best of our knowledge, the highest frequency of SNPs described in woody plant species.</p

    Antileishmanial polyphenols from Corymbia maculata

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    An activity–guided fractionation was used to identify the antileishmanial compounds of Corymbia maculata. The hexane, ethyl acetate and methanol extracts were active in in vitro antileishmanial assay. Twelve polyphenols including 8-demethyl eucalyptin (1), eucalyptin (2), myrciaphenone A (3), myrciaphenone B (4), quercetin-3-O-β-D-xylopyranoside (5), myricetin-3-O-α-L-rhamnopyranoside (6), quercetin-3- O-β-D-galactopyranoside (7), quercetin-3-O-β-D-glucopyranoside (8), quercetin-3-O-α-L-rhamnopyranoside (9), syringic acid (10), gallic acid-3-methyl ether (11), gallic acid-4-methyl ether (12) and gallic acid (13) were isolated from the active extracts. All the tested compounds except 8-demethyleucalyptin and myrciaphenone B showed strong to moderate (6.9–24.5 μM) antileishmanial activity against Leishmania donovani promastigotes. An HPLC-PDA method has been developed to detect/quantify 29 compounds in the extracts of C. maculata leaves. This validated method allows simultaneous quantitation of seven flavonoids, fourteen phloroglucinols and eight other polyphenols and can be applied for qualitative as well as quantitative determination of phytoconstituents in Eucalyptus matrices
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