A bacterial effector protein prevents MAPK-mediated phosphorylation of SGT1 to suppress plant immunity
Fig 5
MAPK-mediated phosphorylation is important for SGT1 function in the activation of ETI.
(A) A phospho-mimic mutation in AtSGT1b T346 (T346D) promotes cell death triggered by RPS2 overexpression in N. benthamiana. Agrobacterium expressing AtSGT1b variants or the GUS-FLAG control (OD600 = 0.5) were infiltrated into N. benthamiana leaves 1 day before infiltration with Agrobacterium expressing RPS2 (OD600 = 0.15). Leaf discs were taken 21 hpi for conductivity measurements at the indicated time points. The time points in the x-axis are indicated as hpi with Agrobacterium expressing RPS2 (mean ± SEM, n = 4, ** p<0.01, t-test, 3 replicates). (B, C) Observation of RPS2-triggered cell death by visible light (B) and UV light (C) in N. benthamiana. The Agrobacterium combinations were infiltrated as described in (A), and the cell death phenotype was recorded 4 dpi with Agrobacterium expressing RPS2. (D, E) A phospho-mimic mutation in AtSGT1b T346 (T346D) disrupts RPS2-SGT1b association in N. benthamiana. Agrobacterium combinations with different constructs were infiltrated in N. benthamiana leaves and luciferase activities were examined in both qualitative (CCD imaging machine, D) and quantitative assays (microplate luminescence reader, E). Quantification of the luciferase signal was performed with microplate luminescence reader (mean ± SEM, n = 8, ** p<0.01, t-test, 3 replicates). The nomenclature of the AtSGT1b mutants used is: 1A = S271A, 1D = S271D, 2A = T346A, 2D = T346D, AA = S271AT346A, DD = S271DT346D. The experiments were performed at least 3 times with similar results.