title: Uncovering the defence responses of Eucalyptus to pests and pathogens in the genomics age.
abstract: Long-lived tree species are subject to attack by various pests and pathogens during their lifetime. This problem is exacerbated by climate change, which may increase the host range for pathogens and extend the period of infestation by pests. Plant defences may involve preformed barriers or induced resistance mechanisms based on recognition of the invader, complex signalling cascades, hormone signalling, activation of transcription factors and production of pathogenesis-related (PR) proteins with direct antimicrobial or anti-insect activity. Trees have evolved some unique defence mechanisms compared with well-studied model plants, which are mostly herbaceous annuals. The genome sequence of Eucalyptus grandis W. Hill ex Maiden has recently become available and provides a resource to extend our understanding of defence in large woody perennials. This review synthesizes existing knowledge of defence mechanisms in model plants and tree species and features mechanisms that may be important for defence in Eucalyptus, such as anatomical variants and the role of chemicals and proteins. Based on the E. grandis genome sequence, we have identified putative PR proteins based on sequence identity to the previously described plant PR proteins. Putative orthologues for PR-1, PR-2, PR-4, PR-5, PR-6, PR-7, PR-8, PR-9, PR-10, PR-12, PR-14, PR-15 and PR-17 have been identified and compared with their orthologues in Populus trichocarpa Torr. & A. Gray ex Hook and Arabidopsis thaliana (L.) Heynh. The survey of PR genes in Eucalyptus provides a first step in identifying defence gene targets that may be employed for protection of the species in future. Genomic resources available for Eucalyptus are discussed and approaches for improving resistance in these hardwood trees, earmarked as a bioenergy source in future, are considered.
authors.affiliation: Department of Genetics, Genomics Research Institute (GRI), Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa; sanushka.naidoo@fabi.up.ac.za.
authors.forename: Sanushka
authors.initials: S
authors.lastname: Naidoo
authors.affiliation: Research School of Biology, Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Carsten
authors.initials: C
authors.lastname: Külheim
authors.affiliation: Department of Genetics, Genomics Research Institute (GRI), Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa;
authors.forename: Lizahn
authors.initials: L
authors.lastname: Zwart
authors.affiliation: Department of Genetics, Genomics Research Institute (GRI), Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa;
authors.forename: Ronishree
authors.initials: R
authors.lastname: Mangwanda
authors.affiliation: Department of Genetics, Genomics Research Institute (GRI), Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa;
authors.forename: Caryn N
authors.initials: CN
authors.lastname: Oates
authors.affiliation: Department of Genetics, Genomics Research Institute (GRI), Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa;
authors.forename: Erik A
authors.initials: EA
authors.lastname: Visser
authors.affiliation: Department of Genetics, Genomics Research Institute (GRI), Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa;
authors.forename: Febé E
authors.initials: FE
authors.lastname: Wilken
authors.affiliation: Department of Genetics, Genomics Research Institute (GRI), Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa;
authors.forename: Thandekile B
authors.initials: TB
authors.lastname: Mamni
authors.affiliation: Department of Genetics, Genomics Research Institute (GRI), Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria 0028, South Africa;
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Myburg
mesh_terms: D005052:Eucalyptus / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D010935:Plant Diseases / Q000209:etiology / Q000276:immunology; D057865:Plant Immunity; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; C053376:pathogenesis-related proteins, plant
keywords: anatomical defences; biotechnology; breeding; genomic resources; phytohormone; plant immunity; terpenoid; transcriptomics