The Ralstonia solanacearum type III effector RipAY targets plant redox regulators to suppress immune responses

• Published in: Molecular plant pathology Vol. 19; no. 1; pp. 129 - 142
• Main Authors: Sang, Yuying, Wang, Yaru, Ni, Hong, Cazalé, Anne‐Claire, She, Yi‐Min, Peeters, Nemo, Macho, Alberto P.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.01.2018; Wiley; John Wiley and Sons Inc
• Subjects: Arabidopsis - immunology; Arabidopsis - microbiology; Bacteria; Bacterial Proteins - metabolism; Biochemical analysis; Cell Nucleus - metabolism; Cysteine - metabolism; gamma-Glutamylcyclotransferase - metabolism; Glutathione; Glutathione - metabolism; Green Fluorescent Proteins - metabolism; Host plants; Immune response; Life Sciences; Nicotiana - cytology; Nicotiana - immunology; Nicotiana - microbiology; Original; Oxidation-Reduction; Pathogens; Plant cells; Plant Cells - metabolism; Plant diseases; Plant Immunity; Plant physiology; Plants (botany); Proteins; Ralstonia; Ralstonia solanacearum; Ralstonia solanacearum - metabolism; Ralstonia solanacearum - pathogenicity; redox; Regulators; Salicylic acid; Signaling; thioredoxin; Thioredoxins - metabolism; type III effector; Type III Secretion Systems - metabolism; Vegetal Biology; Virulence; γ-Glutamylcyclotransferase; thioredoxin; glutathione; type III effector; plant immunity; Ralstonia; redox; ralstonia
• ISSN: 1464-6722; 1364-3703
• DOI: 10.1111/mpp.12504

Summary The subversion of plant cellular functions is essential for bacterial pathogens to proliferate in host plants and cause disease. Most bacterial plant pathogens employ a type III secretion system to inject type III effector (T3E) proteins inside plant cells, where they contribute to the pathogen‐induced alteration of plant physiology. In this work, we found that the Ralstonia solanacearum T3E RipAY suppresses plant immune responses triggered by bacterial elicitors and by the phytohormone salicylic acid. Further biochemical analysis indicated that RipAY associates in planta with thioredoxins from Nicotiana benthamiana and Arabidopsis. Interestingly, RipAY displays γ‐glutamyl cyclotransferase (GGCT) activity to degrade glutathione in plant cells, which is required for the reported suppression of immune responses. Given the importance of thioredoxins and glutathione as major redox regulators in eukaryotic cells, RipAY activity may constitute a novel and powerful virulence strategy employed by R. solanacearum to suppress immune responses and potentially alter general redox signalling in host cells.