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Yang C, Lin Y, Xiang X, Shao D, Qiu Z, Li Y, Wu S. MbEOMT1 regulates methyleugenol biosynthesis in Melaleuca bracteata F. Muell. Tree Physiol 2024; 44:tpae034. [PMID: 38498320 DOI: 10.1093/treephys/tpae034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 01/30/2024] [Accepted: 03/02/2024] [Indexed: 03/20/2024]
Abstract
Methyleugenol, a bioactive compound in the phenylpropene family, undergoes its final and crucial biosynthetic transformation when eugenol O-methyltransferase (EOMT) converts eugenol into methyleugenol. While Melaleuca bracteata F. Muell essential oil is particularly rich in methyleugenol, it contains only trace amounts of its precursor, eugenol. This suggests that the EOMT enzyme in M. bracteata is highly efficient, although it has not yet been characterized. In this study, we isolated and identified an EOMT gene from M. bracteata, termed MbEOMT1, which is primarily expressed in the flowers and leaves and is inducible by methyl jasmonate (MeJA). Subcellular localization of MbEOMT1 in the cytoplasm was detected. Through transient overexpression experiments, we found that MbEOMT1 significantly elevates the concentration of methyleugenol in M. bracteata leaves. Conversely, silencing of MbEOMT1 via virus-induced gene silencing led to a marked reduction in methyleugenol levels. Our in vitro enzymatic assays further confirmed that MbEOMT1 specifically catalyzes the methylation of eugenol. Collectively, these findings establish that the MbEOMT1 gene is critical for methyleugenol biosynthesis in M. bracteata. This study enriches the understanding of phenylpropene biosynthesis and suggests that MbEOMT1 could serve as a valuable catalyst for generating bioactive compounds in the future.
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Affiliation(s)
- Chao Yang
- Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, College of Horticulture, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
- Institute of Natural Products of Horticultural Plants, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
| | - Yongsheng Lin
- College of Life Sciences, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
| | - Xuwen Xiang
- Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, College of Horticulture, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
- Institute of Natural Products of Horticultural Plants, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
| | - Dandan Shao
- Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, College of Horticulture, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
- Institute of Natural Products of Horticultural Plants, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
| | - Ziwen Qiu
- Agricultural Science and Technology Research Center of Chaozhou in Guangdong Province, Qiandong Town, Raoping County, Chaozhou 315600, China
| | - Yongyu Li
- Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, College of Horticulture, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
- Institute of Natural Products of Horticultural Plants, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
| | - Shaohua Wu
- Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, College of Horticulture, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
- Institute of Natural Products of Horticultural Plants, Fujian Agriculture and Forestry University, 15 Shangxiadian Road, Cangshan District, Fuzhou 350002, China
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Zhang X, Xu Z, Liu B, Xiao Y, Chai L, Zhong L, Huo H, Liu L, Yang H, Liu H. Identification of MYB gene family in medicinal tea tree Melaleuca alternifolia (Maiden and Betche) cheel and analysis of members regulating terpene biosynthesis. Mol Biol Rep 2024; 51:70. [PMID: 38175288 DOI: 10.1007/s11033-023-09019-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 10/12/2023] [Indexed: 01/05/2024]
Abstract
BACKGROUND The tea tree (Melaleuca alternifolia) is renowned for its production of tea tree oil, an essential oil primarily composed of terpenes extracted from its shoot. MYB transcription factors, which are one of the largest TF families, play a crucial role in regulating primary and secondary metabolite synthesis. However, knowledge of the MYB gene family in M. alternifolia is limited. METHODS AND RESULTS Here, we conducted a comprehensive genome-wide analysis of MYB genes in M. alternifolia, referred to as MaMYBs, including phylogenetic relationships, structures, promoter regions, and GO annotations. Our findings classified 219 MaMYBs into four subfamilies: one 5R-MYB, four 3R-MYBs, sixty-one MYB-related, and the remaining 153 are all 2R-MYBs. Seven genes (MYB189, MYB146, MYB44, MYB29, MYB175, MYB162, and MYB160) were linked to terpenoid synthesis based on GO annotation. Phylogenetic analysis with Arabidopsis homologous MYB genes suggested that MYB193 and MYB163 may also be involved in terpenoid synthesis. Additionally, through correlation analysis of gene expression and metabolite content, we identified 42 MYB genes associated with metabolite content. CONCLUSION The results provide valuable insights into the importance of MYB transcription factors in essential oil production in M. alternifolia. These findings lay the groundwork for a better understanding of the MYB regulatory network and the development of novel strategies to enhance essential oil synthesis in M. alternifolia.
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Affiliation(s)
- Xiaoning Zhang
- Guangxi Key Laboratory of Special Non-Wood Forest Cultivation and Utilization, Guangxi Forestry Research Institute, Nanning, 530002, China
| | - Zhanwu Xu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, College of Life Sciences, Hubei University, Wuhan, 430062, China
| | - Buming Liu
- Guangxi Key Laboratory of Traditional Chinese Medicine Quality Standards, Guangxi Institute of Chinese Medicine and Pharmaceutical Science, Nanning, 530022, China
| | - Yufei Xiao
- Guangxi Key Laboratory of Special Non-Wood Forest Cultivation and Utilization, Guangxi Forestry Research Institute, Nanning, 530002, China
| | - Ling Chai
- Guangxi Key Laboratory of Traditional Chinese Medicine Quality Standards, Guangxi Institute of Chinese Medicine and Pharmaceutical Science, Nanning, 530022, China
| | - Lianxiang Zhong
- Guangxi Key Laboratory of Special Non-Wood Forest Cultivation and Utilization, Guangxi Forestry Research Institute, Nanning, 530002, China
| | - Heqiang Huo
- Department of Environmental Horticulture, Mid-Florida Research and Education Center, Apopka, 32703, FL, USA
| | - Li Liu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, College of Life Sciences, Hubei University, Wuhan, 430062, China
| | - Hong Yang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, College of Life Sciences, Hubei University, Wuhan, 430062, China.
| | - Hailong Liu
- Guangxi Key Laboratory of Special Non-Wood Forest Cultivation and Utilization, Guangxi Forestry Research Institute, Nanning, 530002, China.
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Voelker J, Mauleon R, Shepherd M. A terpene synthase supergene locus determines chemotype in Melaleuca alternifolia (tea tree). New Phytol 2023; 240:1944-1960. [PMID: 37737003 DOI: 10.1111/nph.19262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 08/22/2023] [Indexed: 09/23/2023]
Abstract
Leaf oil terpenes vary categorically in many plant populations, leading to discrete phenotypes of adaptive and economic significance, but for most species, a genetic explanation for the concerted fluctuation in terpene chemistry remains unresolved. To uncover the genetic architecture underlying multi-component terpene chemotypes in Melaleuca alternifolia (tea tree), a genome-wide association study was undertaken for 148 individuals representing all six recognised chemotypes. A number of single nucleotide polymorphisms in a genomic region of c. 400 kb explained large proportions of the variation in key monoterpenes of tea tree oil. The region contained a cluster of 10 monoterpene synthase genes, including four genes predicted to encode synthases for 1,8-cineole, terpinolene, and the terpinen-4-ol precursor, sabinene hydrate. Chemotype-dependent null alleles at some sites suggested structural variants within this gene cluster, providing a possible basis for linkage disequilibrium in this region. Genotyping in a separate domesticated population revealed that all alleles surrounding this gene cluster were fixed after artificial selection for a single chemotype. These observations indicate that a supergene accounts for chemotypes in M. alternifolia. A genetic model with three haplotypes, encompassing the four characterised monoterpene synthase genes, explained the six terpene chemotypes, and was consistent with available biparental cross-segregation data.
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Affiliation(s)
- Julia Voelker
- Faculty of Science and Engineering, Southern Cross University, Military Road, East Lismore, NSW, 2480, Australia
| | - Ramil Mauleon
- Faculty of Science and Engineering, Southern Cross University, Military Road, East Lismore, NSW, 2480, Australia
| | - Mervyn Shepherd
- Faculty of Science and Engineering, Southern Cross University, Military Road, East Lismore, NSW, 2480, Australia
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Chen SH, Martino AM, Luo Z, Schwessinger B, Jones A, Tolessa T, Bragg JG, Tobias PA, Edwards RJ. A high-quality pseudo-phased genome for Melaleuca quinquenervia shows allelic diversity of NLR-type resistance genes. Gigascience 2022; 12:giad102. [PMID: 38096477 PMCID: PMC10720953 DOI: 10.1093/gigascience/giad102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 09/11/2023] [Accepted: 11/14/2023] [Indexed: 12/17/2023] Open
Abstract
BACKGROUND Melaleuca quinquenervia (broad-leaved paperbark) is a coastal wetland tree species that serves as a foundation species in eastern Australia, Indonesia, Papua New Guinea, and New Caledonia. While extensively cultivated for its ornamental value, it has also become invasive in regions like Florida, USA. Long-lived trees face diverse pest and pathogen pressures, and plant stress responses rely on immune receptors encoded by the nucleotide-binding leucine-rich repeat (NLR) gene family. However, the comprehensive annotation of NLR encoding genes has been challenging due to their clustering arrangement on chromosomes and highly repetitive domain structure; expansion of the NLR gene family is driven largely by tandem duplication. Additionally, the allelic diversity of the NLR gene family remains largely unexplored in outcrossing tree species, as many genomes are presented in their haploid, collapsed state. RESULTS We assembled a chromosome-level pseudo-phased genome for M. quinquenervia and described the allelic diversity of plant NLRs using the novel FindPlantNLRs pipeline. Analysis reveals variation in the number of NLR genes on each haplotype, distinct clustering patterns, and differences in the types and numbers of novel integrated domains. CONCLUSIONS The high-quality M. quinquenervia genome assembly establishes a new framework for functional and evolutionary studies of this significant tree species. Our findings suggest that maintaining allelic diversity within the NLR gene family is crucial for enabling responses to environmental stress, particularly in long-lived plants.
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Affiliation(s)
- Stephanie H Chen
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Kensington NSW 2052, Australia
- Research Centre for Ecosystem Resilience, Botanic Gardens of Sydney, Sydney NSW 2000, Australia
| | - Alyssa M Martino
- School of Life and Environmental Sciences, The University of Sydney, Camperdown NSW 2006, Australia
| | - Zhenyan Luo
- Research School of Biology, The Australian National University, Canberra ACT 2601, Australia
| | - Benjamin Schwessinger
- Research School of Biology, The Australian National University, Canberra ACT 2601, Australia
| | - Ashley Jones
- Research School of Biology, The Australian National University, Canberra ACT 2601, Australia
| | - Tamene Tolessa
- Research School of Biology, The Australian National University, Canberra ACT 2601, Australia
- School of Environment and Rural Science, University of New England, Armidale NSW 2351, Australia
| | - Jason G Bragg
- Research Centre for Ecosystem Resilience, Botanic Gardens of Sydney, Sydney NSW 2000, Australia
- School of Biological, Earth and Environmental Sciences, UNSW Sydney, Kensington NSW 2052, Australia
| | - Peri A Tobias
- School of Life and Environmental Sciences, The University of Sydney, Camperdown NSW 2006, Australia
| | - Richard J Edwards
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Kensington NSW 2052, Australia
- Minderoo OceanOmics Centre at UWA, UWA Oceans Institute, University of Western Australia, Crawley WA 6009, Australia
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Hsieh JF, Chuah A, Patel HR, Sandhu KS, Foley WJ, Külheim C. Transcriptome Profiling of Melaleuca quinquenervia Challenged by Myrtle Rust Reveals Differences in Defense Responses Among Resistant Individuals. Phytopathology 2018; 108:495-509. [PMID: 29135360 DOI: 10.1094/phyto-09-17-0307-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Plants have developed complex defense mechanisms to protect themselves against pathogens. A wide-host-range fungus, Austropuccinia psidii, which has caused severe damage to ecosystems and plantations worldwide, is a major threat to Australian ecosystems dominated by members of the family Myrtaceae. In particular, the east coast wetland foundation tree species Melaleuca quinquenervia, appears to be variably susceptible to this pathogen. Understanding the molecular basis of host resistance would enable better management of this rust disease. We identified resistant and susceptible individuals of M. quinquenervia and explored their differential gene expression in order to discover the molecular basis of resistance against A. psidii. Rust screening of germplasm showed a varying degree of response, with fully resistant to highly susceptible individuals. We used transcriptome profiling in samples collected before and at 5 days postinoculation (dpi). Differential gene expression analysis showed that numerous defense-related genes were induced in susceptible plants at 5 dpi. Mapping reads against the A. psidii genome showed that only susceptible plants contained fungal-derived transcripts. Resistant plants exhibited an overexpression of candidate A. psidii resistance-related genes such as receptor-like kinases, nucleotide-binding site leucine-rich repeat proteins, glutathione S-transferases, WRKY transcriptional regulators, and pathogenesis-related proteins. We identified large differences in the expression of defense-related genes among resistant individuals.
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Affiliation(s)
- Ji-Fan Hsieh
- First, fifth, and sixth authors: Research School of Biology, The Australian National University, 116 Daley Road, Canberra 2601, ACT, Australia; second and third authors: The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra 2601, ACT, Australia; and fourth author: Plant Breeding Institute, The University of Sydney, 107 Cobbitty Road, Cobbitty 2570, NSW, Australia
| | - Aaron Chuah
- First, fifth, and sixth authors: Research School of Biology, The Australian National University, 116 Daley Road, Canberra 2601, ACT, Australia; second and third authors: The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra 2601, ACT, Australia; and fourth author: Plant Breeding Institute, The University of Sydney, 107 Cobbitty Road, Cobbitty 2570, NSW, Australia
| | - Hardip R Patel
- First, fifth, and sixth authors: Research School of Biology, The Australian National University, 116 Daley Road, Canberra 2601, ACT, Australia; second and third authors: The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra 2601, ACT, Australia; and fourth author: Plant Breeding Institute, The University of Sydney, 107 Cobbitty Road, Cobbitty 2570, NSW, Australia
| | - Karanjeet S Sandhu
- First, fifth, and sixth authors: Research School of Biology, The Australian National University, 116 Daley Road, Canberra 2601, ACT, Australia; second and third authors: The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra 2601, ACT, Australia; and fourth author: Plant Breeding Institute, The University of Sydney, 107 Cobbitty Road, Cobbitty 2570, NSW, Australia
| | - William J Foley
- First, fifth, and sixth authors: Research School of Biology, The Australian National University, 116 Daley Road, Canberra 2601, ACT, Australia; second and third authors: The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra 2601, ACT, Australia; and fourth author: Plant Breeding Institute, The University of Sydney, 107 Cobbitty Road, Cobbitty 2570, NSW, Australia
| | - Carsten Külheim
- First, fifth, and sixth authors: Research School of Biology, The Australian National University, 116 Daley Road, Canberra 2601, ACT, Australia; second and third authors: The John Curtin School of Medical Research, The Australian National University, 131 Garran Road, Canberra 2601, ACT, Australia; and fourth author: Plant Breeding Institute, The University of Sydney, 107 Cobbitty Road, Cobbitty 2570, NSW, Australia
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Padovan A, Keszei A, Hassan Y, Krause ST, Köllner TG, Degenhardt J, Gershenzon J, Külheim C, Foley WJ. Four terpene synthases contribute to the generation of chemotypes in tea tree (Melaleuca alternifolia). BMC Plant Biol 2017; 17:160. [PMID: 28978322 PMCID: PMC5628445 DOI: 10.1186/s12870-017-1107-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 09/27/2017] [Indexed: 06/07/2023]
Abstract
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.
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Affiliation(s)
- Amanda Padovan
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, 2601 Australia
| | - Andras Keszei
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, 2601 Australia
| | - Yasmin Hassan
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, 2601 Australia
| | - Sandra T. Krause
- Institute of Pharmacy, Martin Luther University, Hoher Weg 8, 06120 Halle, Germany
| | - Tobias G. Köllner
- Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany
| | - Jörg Degenhardt
- Institute of Pharmacy, Martin Luther University, Hoher Weg 8, 06120 Halle, Germany
| | - Jonathan Gershenzon
- Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany
| | - Carsten Külheim
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, 2601 Australia
| | - William J. Foley
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, 2601 Australia
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Bustos-Segura C, Padovan A, Kainer D, Foley WJ, Külheim C. Transcriptome analysis of terpene chemotypes of Melaleuca alternifolia across different tissues. Plant Cell Environ 2017; 40:2406-2425. [PMID: 28771760 DOI: 10.1111/pce.13048] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 07/25/2017] [Accepted: 07/26/2017] [Indexed: 06/07/2023]
Abstract
Plant chemotypes or chemical polymorphisms are defined by discrete variation in secondary metabolites within a species. This variation can have consequences for ecological interactions or the human use of plants. Understanding the molecular basis of chemotypic variation can help to explain how variation of plant secondary metabolites is controlled. We explored the transcriptomes of the 3 cardinal terpene chemotypes of Melaleuca alternifolia in young leaves, mature leaves, and stem and compared transcript abundance to variation in the constitutive profile of terpenes. Leaves from chemotype 1 plants (dominated by terpinen-4-ol) show a similar pattern of gene expression when compared to chemotype 5 plants (dominated by 1,8-cineole). Only terpene synthases in young leaves were differentially expressed between these chemotypes, supporting the idea that terpenes are mainly synthetized in young tissue. Chemotype 2 plants (dominated by terpinolene) show a greater degree of differential gene expression compared to the other chemotypes, which might be related to the isolation of plant populations that exhibit this chemotype and the possibility that the terpinolene synthase gene in M. alternifolia was derived by introgression from a closely related species, Melaleuca trichostachya. By using multivariate analyses, we were able to associate terpenes with candidate terpene synthases.
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Affiliation(s)
- Carlos Bustos-Segura
- Division of Evolution and Ecology, Research School of Biology, The Australian National University, Canberra, 2601, Australian Capital Territory, Australia
- Laboratory of Evolutionary Entomology, Institute of Biology, University of Neuchatel, Neuchatel, 2000, Switzerland
| | - Amanda Padovan
- Division of Evolution and Ecology, Research School of Biology, The Australian National University, Canberra, 2601, Australian Capital Territory, Australia
| | - David Kainer
- Division of Evolution and Ecology, Research School of Biology, The Australian National University, Canberra, 2601, Australian Capital Territory, Australia
| | - William J Foley
- Division of Evolution and Ecology, Research School of Biology, The Australian National University, Canberra, 2601, Australian Capital Territory, Australia
| | - Carsten Külheim
- Division of Evolution and Ecology, Research School of Biology, The Australian National University, Canberra, 2601, Australian Capital Territory, Australia
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Chong C, Edwards W, Pearson R, Waycott M. Sprouting and genetic structure vary with flood disturbance in the tropical riverine paperbark tree, Melaleuca leucadendra (Myrtaceae). Am J Bot 2013; 100:2250-2260. [PMID: 24186959 DOI: 10.3732/ajb.1200614] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
PREMISE OF THE STUDY Sprouting in woody plants promotes persistence in the face of disturbance, ultimately influencing population structure. Different disturbance regimes drive variable population responses, but there have been few direct tests of the relative differences in population structure to specific drivers. We measured population structure as genotypic diversity (clonality) as a function of hydrological regime for a riverine tree, Melaleuca leucadendra, a major structural component in flood landscapes in the Australian dry tropics. METHODS We estimated clonality, genotypic richness, and population allelic diversity. The relationship among disturbance, genetic estimates of clonality, and population distinctiveness was compared with flood regime, characterized by return frequencies and hydrological stress at individual river reaches. KEY RESULTS Two contrasting patterns of genotypic structure were detected and corresponded to order-of-magnitude differences in flood regime between sites. At mainstem locations characterized by greatest flood intensity, sprouting generated clonal structure to 17 m (30% ramets clonal). By contrast, clonality was atypical at lower-disturbance tributaries (0% clonal). Population allelic distributions showed extensive genetic exchange among mainstem locations, but strong genetic differentiation between mainstem and tributaries. CONCLUSIONS Population structure and distinctiveness in riverine Melaleuca are determined by differences in sprouting and recruitment responses that depend on localized hydrological regime. Sprouting contributes to population persistence via localized clonal growth. Resprouting following disturbance in M. leucadendra may help explain its numerical dominance in tropical river systems. This study, although preliminary, suggests that flood ecosystems may represent excellent experimental systems to develop a better understanding of whole-organism responses to environmental drivers.
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Affiliation(s)
- Caroline Chong
- School of Marine and Tropical Biology, James Cook University, Townsville, QLD 4811, Australia
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Webb H, Lanfear R, Hamill J, Foley WJ, Külheim C. The yield of essential oils in Melaleuca alternifolia (Myrtaceae) is regulated through transcript abundance of genes in the MEP pathway. PLoS One 2013; 8:e60631. [PMID: 23544156 PMCID: PMC3609730 DOI: 10.1371/journal.pone.0060631] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 03/01/2013] [Indexed: 01/29/2023] Open
Abstract
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.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.
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Affiliation(s)
- Hamish Webb
- Research School of Biology, Australian National University, Canberra, ACT, Australia
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Robert Lanfear
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - John Hamill
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - William J. Foley
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Carsten Külheim
- Research School of Biology, Australian National University, Canberra, ACT, Australia
- * E-mail:
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Shelton D, Zabaras D, Chohan S, Wyllie SG, Baverstock P, Leach D, Henry R. Isolation and partial characterisation of a putative monoterpene synthase from Melaleuca alternifolia. Plant Physiol Biochem 2004; 42:875-82. [PMID: 15694281 DOI: 10.1016/j.plaphy.2004.10.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Accepted: 10/25/2004] [Indexed: 05/01/2023]
Abstract
Melaleuca alternifolia (Cheel) is an Australia native tree harvested for its monoterpene-rich, essential oil. Monoterpene synthases (E.C. 4.2.3.20) were partially purified from the flush growth of the commercially important, high terpinen-4-ol chemotype of M. alternifolia. The purified fractions produced an acyclic monoterpene, linalool that is not present in the essential oil. To further characterise the monoterpene synthase, a cDNA library was constructed and 500 expressed sequence tags (ESTs) were sequenced to isolate putative terpene synthases. A single clone with similarity to the TspB gene sub-family of angiosperm monoterpene and isoprene synthases was isolated but was truncated at the 5' end. This single clone was used to design a probe for a cDNA library and was applied to isolate a full-length clone. This gene encoded a polypeptide 583 amino acids in length (67 kDa) including a putative transit peptide. Heterologous expression of the gene in Escherichia coli and subsequent assay of the recombinant enzyme did not result in the production of terpinen-4-ol, the major constituent of tea tree oil, or of its precursor sabinene hydrate. Significant quantities of linalool were observed in these assays, and in the assays of monoterpene synthase activity of a native enzyme in vitro, but the racemic nature of the linalool means that it may have a non-enzymatic origin.
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Affiliation(s)
- Dale Shelton
- Centre for Plant Conservation Genetics, Southern Cross University, Lismore, NSW 2480, Australia.
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