AUTHOR=N’Guyen Guillaume Quang , Raulo Roxane , Porquier Antoine , Iacomi Beatrice , Pelletier Sandra , Renou Jean-Pierre , Bataillé-Simoneau Nelly , Campion Claire , Hamon Bruno , Kwasiborski Anthony , Colou Justine , Benamar Abdelilah , Hudhomme Pietrick , Macherel David , Simoneau Philippe , Guillemette Thomas TITLE=Responses of the Necrotrophic Fungus Alternaria brassisicola to the Indolic Phytoalexin Brassinin JOURNAL=Frontiers in Plant Science VOLUME=11 YEAR=2021 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.611643 DOI=10.3389/fpls.2020.611643 ISSN=1664-462X ABSTRACT=

Alternaria brassicicola causes black spot disease in Brassicaceae. During host infection, this necrotrophic fungus is exposed to various antimicrobial compounds, such as the phytoalexin brassinin which is produced by many cultivated Brassica species. To investigate the cellular mechanisms by which this compound causes toxicity and the corresponding fungal adaptive strategies, we first analyzed fungal transcriptional responses to short-term exposure to brassinin and then used additional functional approaches. This study supports the hypothesis that indolic phytoalexin primarily targets mitochondrial functions in fungal cells. Indeed, we notably observed that phytoalexin treatment of A. brassicicola disrupted the mitochondrial membrane potential and resulted in a significant and rapid decrease in the oxygen consumption rates. Secondary effects, such as Reactive oxygen species production, changes in lipid and endoplasmic reticulum homeostasis were then found to be induced. Consequently, the fungus has to adapt its metabolism to protect itself against the toxic effects of these molecules, especially via the activation of high osmolarity glycerol and cell wall integrity signaling pathways and by induction of the unfolded protein response.