Phosphorylation of HopQ1, a Type III Effector from Pseudomonas syringae, Creates a Binding Site for Host 14-3-3 Proteins      

Abstract

HopQ1 (for Hrp outer protein Q), a type III effector secreted by Pseudomonas syringae pv phaseolicola, is widely conserved among diverse genera of plant bacteria. It promotes the development of halo blight in common bean (Phaseolus vulgaris). However, when this same effector is injected into Nicotiana benthamiana cells, it is recognized by the immune system and prevents infection. Although the ability to synthesize HopQ1 determines host specificity, the role it plays inside plant cells remains unexplored. Following transient expression in planta, HopQ1 was shown to copurify with host 14-3-3 proteins. The physical interaction between HopQ1 and 14-3-3a was confirmed in planta using the fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy technique. Moreover, mass spectrometric analyses detected specific phosphorylation of the canonical 14-3-3 binding site (RSXpSXP, where pS denotes phosphoserine) located in the amino-terminal region of HopQ1. Amino acid substitution within this motif abrogated the association and led to altered subcellular localization of HopQ1. In addition, the mutated HopQ1 protein showed reduced stability in planta. These data suggest that the association between host 14-3-3 proteins and HopQ1 is important for modulating the properties of this bacterial effector.

Cell Wall Degrading Enzyme Induced Rice Innate Immune Responses Are Suppressed by the Type 3 Secretion System Effectors XopN, XopQ, XopX and XopZ of Xanthomonas oryzae pv. oryzae

“…The ARM/HEAT repeats are typically found in eukaryotic proteins that function in diverse cellular signaling networks such as Arabidopsis homologs of nuclear transport protein importin-β [31] and AtCAND1 which functions in regulation of auxin signaling [32]. Furthermore, it has been shown that different isoforms of 14-3-3s interact with bacterial effector proteins in various plant-pathogen interactions to modulate plant innate immunity [30,33,34]. It is possible that the XopN protein of X .…”

Emerging role of SGT1 as a regulator of NB-LRR-receptor nucleocytoplasmic partitioning

“…However no significant reduction in steady-state levels of GFP-Rx or 4HA-GFP-Rx was observed in SGT1 -silenced plants compared with that in controls 6 . We have observed that GFP-like tags may stabilize protein constructs expressed in planta 7 . Alternatively, SGT1 might affect the conformation or act directly on translocation of Rx.…”

The bacterial effector HopM1 suppresses PAMP‐triggered oxidative burst and stomatal immunity

“…An increasing body of evidence points at a role of 14‐3‐3s in plant immunity: the tomato 14‐3‐3 protein 7 (TFT7) regulates immunity‐associated cell death by enhancing the protein accumulation and signalling ability of MAPKKK alpha, and interacts with this MAPKKK and the MAPKK SlMKK2 (Oh et al ., ; Oh & Martin, ); the Pto DC3000 effector HopQ1 targets TFT5 and TFT7 and interacts with these 14‐3‐3s in a phosphorylation‐dependent manner (Giska et al ., ; Li et al ., ); in rice, the 14‐3‐3 protein GF14e acts as a negative regulator of cell death and disease resistance (Manosalva et al ., ); and the effector XopN from Xhantomonas campestris pv vesicatoria targets the tomato 14‐3‐3 isoform TFT1, the Arabidopsis GRF8 orthologue, to promote bacterial pathogenesis (Taylor et al ., ). The full extent of the role of different 14‐3‐3s in defence and immunity, however, still needs to be further explored.…”