A bacterial effector protein prevents MAPK-mediated phosphorylation of SGT1 to suppress plant immunity

• Published in: PLoS pathogens Vol. 16; no. 9; p. e1008933
• Main Authors: Yu, Gang, Xian, Liu, Xue, Hao, Yu, Wenjia, Rufian, Jose S, Sang, Yuying, Morcillo, Rafael J L, Wang, Yaru, Macho, Alberto P
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.09.2020; Public Library of Science (PLoS)
• Subjects: Accumulation; Bacterial Proteins - metabolism; Binding sites; Biology; Biology and Life Sciences; Botanical research; Cell death; Cellular proteins; Disease resistance (Plants); Domains; Feedback loops; Health aspects; Immune response; Immune system; Immunity; Infections; Kinases; Leucine; MAP kinase; Medicine and Health Sciences; Mitogen-activated protein kinases; Mitogen-Activated Protein Kinases - metabolism; Nicotiana - metabolism; Nucleotides; Pathogens; Phosphorylation; Physiological aspects; Plant Diseases - immunology; Plant immunity; Plant Immunity - immunology; Plant Proteins - immunology; Plant Proteins - metabolism; Plant sciences; Plant-pathogen relationships; Positive feedback; Proteins; Ralstonia solanacearum - immunology; Ralstonia solanacearum - metabolism; Research and Analysis Methods; Survival analysis; Virulence; China; Beijing China
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1008933

Nucleotide-binding domain and leucine-rich repeat-containing (NLR) proteins function as sensors that perceive pathogen molecules and activate immunity. In plants, the accumulation and activation of NLRs is regulated by SUPPRESSOR OF G2 ALLELE OF skp1 (SGT1). In this work, we found that an effector protein named RipAC, secreted by the plant pathogen Ralstonia solanacearum, associates with SGT1 to suppress NLR-mediated SGT1-dependent immune responses, including those triggered by another R. solanacearum effector, RipE1. RipAC does not affect the accumulation of SGT1 or NLRs, or their interaction. However, RipAC inhibits the interaction between SGT1 and MAP kinases, and the phosphorylation of a MAPK target motif in the C-terminal domain of SGT1. Such phosphorylation is enhanced upon activation of immune signaling and contributes to the activation of immune responses mediated by the NLR RPS2. Additionally, SGT1 phosphorylation contributes to resistance against R. solanacearum. Our results shed light onto the mechanism of activation of NLR-mediated immunity, and suggest a positive feedback loop between MAPK activation and SGT1-dependent NLR activation.