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Friend or foe: The genetics of an endophytic tree pathogen infection

Bernard Slippers: Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria

<div>A poorly understood aspect of plant biology is the role played by fungal endophytes that infect healthy plant tissues without inducing symptoms. The fungus <em>Botryosphaeria</em> <em>dothidea</em> has been recognised both as an endophyte and a pathogen on a wide range of woody plant species. It is not known how <em>B. dothidea</em> is able to infect its hosts without triggering a host defence response. In this study, transcriptome data were used to investigate the molecular responses of <em>E. grandis</em> and <em>B. dothidea</em> during an active infection at 24 hours, 48 hours and 7 days post-infection. A weak host response was observed at 48 hours, characterised by the differential expression of 129 genes, which included the up-regulation and down-regulation of key defence genes such as the jasmonate/ethylene transcription factor, <em>MYB15</em>, and the salicylic acid receptor, <em>NPR5</em>, respectively. Data from differential expression analyses of the <em>B. dothidea in planta</em> transcriptome revealed the expression of genes involved in nutrient acquisition, detoxification and cell wall degradation. Transcriptome data suggested that this tree-endophyte interaction is one of tolerance regardless of the weak plant defence response observed. The study provides powerful hypotheses to further explore the importance of fungal tree endophytes.</div>