title: Evidence for salicylic acid signalling and histological changes in the defence response of Eucalyptus grandis to Chrysoporthe austroafricana.
abstract: Eucalyptus species are cultivated for forestry and are of economic importance. The fungal stem canker pathogen Chrysoporthe austroafricana causes disease of varying severity on E. grandis. The Eucalyptus grandis-Chrysoporthe austroafricana interaction has been established as a model system for studying Eucalyptus antifungal defence. Previous studies revealed that the phytohormone salicylic acid (SA) affects the levels of resistance in highly susceptible (ZG14) and moderately resistant (TAG5) clones. The aims of this study were to examine histochemical changes in response to wounding and inoculation as well as host responses at the protein level. The anatomy and histochemical changes induced by wounding and inoculation were similar between the clones, suggesting that anatomical differences do not underlie their different levels of resistance. Tyloses and gum-like substances were present after inoculation and wounding, but cell death occurred only after inoculation. Hyphae of C. austroafricana were observed inside dead and living cells, suggesting that the possibility of a hemibiotrophic interaction requires further investigation. Proteomics analysis revealed the possible involvement of proteins associated with cell death, SA signalling and systemic resistance. In combination with previous information, this study forms a basis for future functional characterisation of candidate genes involved in resistance of E. grandis to C. austroafricana.
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), Genomics Research Institute (GRI), University of Pretoria, Pretoria, South Africa.
authors.forename: Lizahn
authors.initials: L
authors.lastname: Zwart
authors.affiliation: Department of Plant and Soil Sciences, Forestry and Agricultural Biotechnology Institute (FABI), Genomics Research Institute (GRI), University of Pretoria, Pretoria, South Africa.
authors.forename: Dave Kenneth
authors.initials: DK
authors.lastname: Berger
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa.
authors.forename: Lucy Novungayo
authors.initials: LN
authors.lastname: Moleleki
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), Genomics Research Institute (GRI), University of Pretoria, Pretoria, South Africa.
authors.forename: Nicolaas A
authors.initials: NA
authors.lastname: van der Merwe
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), Genomics Research Institute (GRI), University of Pretoria, Pretoria, South Africa.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Myburg
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), Genomics Research Institute (GRI), University of Pretoria, Pretoria, South Africa.
authors.forename: Sanushka
authors.initials: S
authors.lastname: Naidoo
mesh_terms: D001203:Ascomycota / Q000378:metabolism*; D003517:Cyclopentanes / Q000378:metabolism; D060467:Disease Resistance / Q000276:immunology*; D005052:Eucalyptus / Q000378:metabolism / Q000382:microbiology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D054883:Oxylipins / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism
chemical_list: D003517:Cyclopentanes; D054883:Oxylipins; D010937:Plant Growth Regulators; C011006:jasmonic acid; D020156:Salicylic Acid