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.

Impact of Botryosphaeria, Diplodia and Neofusicoccum species on two Eucalyptus species and a hybrid: From pathogenicity to physiological performance

“…This suggestion aligns with the data from mortality and higher variability in lesions registered in E. nitens obtained from seeds, thus presenting variable genetic background. This variability may lead to changes in both chemical composition (Stackpole, Vaillancourt, Alves, Rodrigues, & Potts, 2011) and anatomy (Smith, Pinkard, Hunter, Wingfield, & Mohammed, 2006), which condition plant defences (reviewed by Naidoo et al, 2014). A common plant response to pathogen attack is the downregulation of photosynthesis and imbalances in other processes associated with primary metabolism that are essential to appropriately allocate energy between growth and defence (Berger et al, 2007; Rojas, Senthil-Kumar, Tzin, & Mysore, 2014).…”

“…Félix et al, 2017). This variability may lead to changes in both chemical composition (Stackpole, Vaillancourt, Alves, Rodrigues, & Potts, 2011) and anatomy (Smith, Pinkard, Hunter, Wingfield, & Mohammed, 2006), which condition plant defences (reviewed by Naidoo et al, 2014). In some studies, B. dothidea was usually described as pathogenic to eucalypts (Bettucci & Alonso, 1997;Smith et al, 1994), but we know that this fungus is uncommon and weakly pathogenic or non-pathogenic to these plants (Barradas et al, 2016;Pavlic et al, 2007;Rodas et al, 2009 (Balmelli, Simeto, Marroni, Altier, & Diez, 2014).…”

“…Despite a high adaptability to a broad range of environments, eucalypt plantation ranges are challenged by climate changes and biotic threats (Booth, 2013;Naidoo et al, 2014;Wingfield, Brockerhoff, Wingfield, & Slippers, 2015). Despite a high adaptability to a broad range of environments, eucalypt plantation ranges are challenged by climate changes and biotic threats (Booth, 2013;Naidoo et al, 2014;Wingfield, Brockerhoff, Wingfield, & Slippers, 2015).…”

Phenolics metabolism provides a tool for screening drought tolerant Eucalyptus grandis hybrids

“…Plants exhibiting this disease show deteriorated health, which in some severe cases can lead premature death (Leite et al, 2014;Ross and Brack, 2015). Some pests and pathogens attack plants, specifically, long-lived trees such as Eucalyptus species, which attempt to defend themselves over their whole lifetime against invaders (Naidoo et al, 2014;Jesus et al, 2015). One of the mechanism by which plants evade these threatens in nature is via the accumulation of phytoalexins, which are antimicrobial compounds synthesized mainly through the phenylpropanoid metabolic pathway.…”

Enfermedades bacterianas de eucaliptos: Estado actual del conocimiento

“…ha ido en aumento a nivel mundial, superando actualmente los 20 millones de hectáreas (Naidoo et al 2014). Sin embargo, pese a la exitosa producción forestal, en los últimos años, se ha observado un aumento de las problemáticas sanitarias.…”