Reactive oxygen species generated in chloroplasts contribute to tobacco leaf infection by the necrotrophic fungus Botrytis cinerea.
Rossi, F. R., Krapp, A. R., Bisaro, F., Maiale, S. J., Pieckenstain, F. L. and Carrillo, N.
Instituto de Investigaciones Biotecnologicas-Instituto Tecnologico Chascomus Universidad Nacional de General San Martin, Consejo Nacional de Investigaciones Cientificas y Tecnicas (IIB-INTECH/UNSAM-CONICET), Chascomus, Argentina.
Instituto de Biologia Molecular y Celular de Rosario (IBR-UNR/CONICET), Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario (UNR), Rosario, Argentina.
Reactive oxygen species (ROS) play fundamental roles in plant responses to pathogen infection, including modulation of cell death processes and defense-related gene expression. Cell death triggered as part of the hypersensitive response enhances resistance to biotrophic pathogens, but favors virulence of necrotrophs. Even though the involvement of ROS in the orchestration of defense responses is well established, the relative contribution of specific subcellular ROS sources to plant resistance against microorganisms with different pathogenesis strategies is not completely known. The aim of this work was to investigate the role of chloroplastic ROS in plant defense against a typical necrotrophic fungus, Botrytis cinerea. For this purpose, we used transgenic tobacco lines expressing a plastid-targeted cyanobacterial flavodoxin (pfld lines), which accumulate lower chloroplastic ROS in response to different stresses. Tissue damage and fungal growth were significantly reduced in infected leaves of pfld plants, as compared to infected wild-type (WT) counterparts. ROS build-up triggered by Botrytis infection and associated to chloroplasts was significantly decreased (70-80%) in pfld leaves relative to the wild type. Phytoalexin accumulation and expression of pathogenesis-related genes were induced to a lower degree in pfld plants than in WT siblings. The impact of fungal infection on photosynthetic activity was also lower in pfld leaves. The results indicate that chloroplast-generated ROS play a major role in lesion development during Botrytis infection. This work demonstrates that the modulation of chloroplastic ROS levels by expression of a heterologous antioxidant protein can provide a significant degree of protection against a canonical necrotrophic fungus. This article is protected by copyright. All rights reserved.
Plant Journal 92(5): 761-773 (2017)