Nuclear Localization of HopA1Pss61 Is Required for Effector-Triggered Immunity

Abstract

Plant resistance proteins recognize cognate pathogen avirulence proteins (also named effectors) to implement the innate immune responses called effector-triggered immunity. Previously, we reported that hopA1 from Pseudomonas syringae pv. syringae strain 61 was identified as an avr gene for Arabidopsis thaliana. Using a forward genetic screen approach, we cloned a hopA1-specific TIR-NBS-LRR class disease resistance gene, RESISTANCE TO PSEUDOMONAS SYRINGAE6 (RPS6). Many resistance proteins indirectly recognize effectors, and RPS6 is thought to interact with HopA1Pss61 indirectly by surveillance of an effector target. However, the involved target protein is currently unknown. Here, we show RPS6 is the only R protein that recognizes HopA1Pss61 in Arabidopsis wild-type Col-0 accession. Both RPS6 and HopA1Pss61 are co-localized to the nucleus and cytoplasm. HopA1Pss61 is also distributed in plasma membrane and plasmodesmata. Interestingly, nuclear localization of HopA1Pss61 is required to induce cell death as NES-HopA1Pss61 suppresses the level of cell death in Nicotiana benthamiana. In addition, in planta expression of hopA1Pss61 led to defense responses, such as a dwarf morphology, a cell death response, inhibition of bacterial growth, and increased accumulation of defense marker proteins in transgenic Arabidopsis. Functional characterization of HopA1Pss61 and RPS6 will provide an important piece of the ETI puzzle.

HopA1 Effector from Pseudomonas syringae pv syringae Strain 61 Affects NMD Processes and Elicits Effector-Triggered Immunity

“…Tobacco is an easy genetic system to use in expression assays via Agrobacterium . Transient expression of HopA1 pss induces strong HR in N. tabacum cv Xanthi and N. benthamiana [ 20 , 29 , 30 ]. With 57% amino acid identity to HopA1 pss , HopA1 pst does not elicit HR in N. benthamiana [ 30 ].…”

“…Transient expression of HopA1 pss induces strong HR in N. tabacum cv Xanthi and N. benthamiana [ 20 , 29 , 30 ]. With 57% amino acid identity to HopA1 pss , HopA1 pst does not elicit HR in N. benthamiana [ 30 ]. However, when we transiently expressed via Agrobacterium , the binary vector clones of Myc-HopA1 pss or Myc-HopA1 pst in N. tabacum , both HopA1s triggered HR ( Figure 1 a).…”

“…HopA1 pss elicits RPS6 -dependent ETI whereas HopA1 pst does not [ 22 , 30 ]. How HopA1 pst evades detection and subsequent ETI elicitation is not known.…”

Conserved Opposite Functions in Plant Resistance to Biotrophic and Necrotrophic Pathogens of the Immune Regulator SRFR1

“…Two leaf discs collected from tomato tissues with a cork borer (No. 5) were ground in 50 µL of 8 M urea buffer to extract total protein, as described previously [ 49 ]. Plant debris was centrifuged twice at 12,000 rpm for 10 min, and the collected supernatant was separated on 12% polyacrylamide gel.…”

Genome Editing for Plasmodesmal Biology

“…Furthermore, the mechanism of HopO1-1-enhanced PD permeability seems to be PDLP5/PDLP7-regulated callose accumulation-dependent. In addition to HopO1-1, recent studies reported that several effectors from P. syringae not only localized at PD, but they also moved symplastically between the cells through these channels ( Kang et al, 2021 ; Li et al, 2021 ). It was also suggested that the intercellular movement of effectors is PD permeability dependent manner ( Li et al, 2021 ).…”