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

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.

Age-associated shifts in cardiac gene transcription and transcriptional responses to ischemic stress.

Aged hearts exhibit reduced tolerance to ischemia-reperfusion, together with altered structure and post-ischemic remodelling. The molecular bases of such changes are unclear. Using cDNA microarrays and quantitative RT-PCR we characterized shifts in gene expression patterns with aging in normoxic and post-ischemic (20 min global ischemia, 60 min reperfusion) murine hearts (young: 2-4 months; aged: 16-18 months). We identified an age-associated up-regulation of transcripts involved in cell death, oxygen transport and metabolism in normoxic hearts. Down-regulated transcripts were involved in transporter activity, protein binding and hydrolase activity, changes in MAPK, WNT and TGF-beta signalling with aging were also observed. Ischemic stress generated a much greater degree of contractile impairment and cellular damage in aged vs. young hearts. This was associated with a substantially modified transcriptional response, with selective changes in Ca2+, WNT, NOTCH and G-protein coupled receptor signalling paths in aged vs. young hearts. Despite some common responses to ischemia in young and aged hearts (induction of heat shock protein transcripts), aging selectively modified ischemic responses of immediate early genes, and genes involved in modulating apoptosis and remodelling/angiogenesis. In summary, aging is associated with shifts in cardiovascular gene expression consistent with the phenotypic features of older hearts. Reduced tolerance with age may be related to modification of signalling (particularly WNT and TGF-beta), and shifts in expression of immediate early genes, and genes important in control of cell death/survival, angiogenesis, and cardiac remodelling.

Investigation of a neuronal nitric oxide synthase gene (NOS1) polymorphism in a multiple sclerosis population.

Multiple Sclerosis (MS) is a chronic neurological disease characterized by demyelination associated with infiltrating white blood cells in the central nervous system (CNS). Nitric oxide synthases (NOS) are a family of enzymes that control the production of nitric oxide. It is possible that neuronal NOS could be involved in MS pathophysiology and hence the nNOS gene is a potential candidate for involvement in disease susceptibility. The aim of this study was to determine whether allelic variation at the nNOS gene locus is associated with MS in an Australian cohort. DNA samples obtained from a Caucasian Australian population affected with MS and an unaffected control population, matched for gender, age and ethnicity, were genotyped for a microsatellite polymorphism in the promoter region of the nNOS gene. Allele frequencies were compared using chi-squared based statistical analyses with significance tested by Monte Carlo simulation. Allelic analysis of MS cases and controls produced a chi-squared value of 5.63 with simulated P = 0.96 (OR(max) = 1.41, 95% CI: 0.926-2.15). Similarly, a Mann-Whitney U analysis gave a non-significant P-value of 0.377 for allele distribution. No differences in allele frequencies were observed for gender or clinical course subtype (P > 0.05). Statistical analysis indicated that there is no association of this nNOS variant and MS and hence the gene does not appear to play a genetically significant role in disease susceptibility.