The identification and differential expression of Eucalyptus grandis pathogenesis-related genes in response to salicylic acid and methyl jasmonate

Abstract

Two important role players in plant defence response are the phytohormones salicylic acid (SA) and jasmonic acid (JA); both of which have been well described in model species such as Arabidopsis thaliana. Several pathogenesis related (PR) genes have previously been used as indicators of the onset of SA and JA signaling in Arabidopsis. This information is lacking in tree genera such as Eucalyptus. The aim of this study was to characterize the transcriptional response of PR genes (EgrPR2, EgrPR3, EgrPR4, EgrPR5, and EgrLOX) identified in Eucalyptus grandis to SA and methyl jasmonate (MeJA) treatment as well as to qualify them as diagnostic for the two signaling pathways. Using the genome sequence of E. grandis, we identified candidate Eucalyptus orthologs EgrPR2, EgrPR3, EgrPR4, EgrPR5, and EgrLOX based on a co-phylogenetic approach. The expression of these genes was investigated after various doses of SA and MeJA (a derivative of JA) treatment as well as at various time points. The transcript levels of EgrPR2 were decreased in response to high concentrations of MeJA whereas the expression of EgrPR3 and EgrLOX declined as the concentrations of SA treatment increased, suggesting an antagonistic relationship between SA and MeJA. Our results support EgrPR2 as potentially diagnostic for SA and EgrPR3, EgrPR4, and EgrLOX as indicators of MeJA signaling. To further validate the diagnostic potential of the PR genes we challenged E. grandis clones with the fungal necrotrophic pathogen Chrysoporthe austroafricana. The tolerant clone showed high induction of EgrPR2 and decreased transcript abundance of EgrPR4. Pre-treatment of the susceptible genotype with 5 mM SA resulted in lesion lengths comparable to the tolerant genotype after artificial inoculation with C. austroafricana. Thus expression profiling of EgrPR2 and EgrPR4 genes could serve as a useful diagnostic approach to determine which of the two signaling pathways are activated against various pathogens in Eucalyptus.

Salicylic acid application modulates physiological and hormonal changes in Eucalyptus globulus under water deficit

“…65 Research on SA application and water deficit tolerance in 66 Eucalyptus species remains completely absent. The existing studies 67 mainly focus on the responses to biotic stress drivers, namely 68 bacteria (Ran et al, 2004) and fungi (Naidoo et al, 2013). Bearing prone areas (Correia et al, 2014a according to Sims and Gamon (2002).…”

Reducing the Harmful Effects of Sanitary Water on Growth and Quality of Some Economic Trees Using Jasmine Oil

“…It is able to regulate ethylene biosynthesis, reduce injuries of the environmental stresses, induce stomatal closure (Kondo, 2010) and decrease chilling injury (Gonzalez-Aquilar et al, 2003). The previous gains, however were supported by those of Naidoo et al (2013) on Eucalyptus grandis, Boeckler et al (2013) on Populus nigra and Sunil et al (2014) on loquat.…”

“…This was emphasized by Naidoo et al (2013) on Eucalyptus grandis, on Pinus pinaster, Semiz et al (2012) on Pinus sylvestris and Quercus ilex, Boeckler et al (2013) on Populus nigra and Lombardero et al (2013) on Pinus pinaster and P. radiata. Furthermore, Kondo (2010) mentioned that jasmonates are able to regulate ethylene biosynthesis and aroma volatiles in the skin of apples and pears, and increased ester and alcohol production in fruits.…”

Signals that stop the rot: Regulation of secondary metabolite defences in cereals

“…Many of these studies have been based on the application of exogenous plant hormones, which is used as an experimental proxy for endogenous hormone levels [96]. However, this approach suffers several limitations, namely that (i) the absorbed hormone concentrations may not be biologically relevant; (ii) co-application of two hormones may not result in the same ratios inside the cells; and (iii) the chemical form of the hormone applied (e.g.…”