A bacterial acetyltransferase triggers immunity in Arabidopsis thaliana independent of hypersensitive response

Abstract

Type-III secreted effectors (T3Es) play critical roles during bacterial pathogenesis in plants. Plant recognition of certain T3Es can trigger defence, often accompanied by macroscopic cell death, termed the hypersensitive response (HR). Economically important species of kiwifruit are susceptible to Pseudomonas syringae pv. actinidiae (Psa), the causal agent of kiwifruit bacterial canker. Although Psa is non-pathogenic in Arabidopsis thaliana, we observed that a T3E, HopZ5 that is unique to a global outbreak clade of Psa, triggers HR and defence in Arabidopsis accession Ct-1. Ws-2 and Col-0 accessions are unable to produce an HR in response to Pseudomonas-delivered HopZ5. While Ws-2 is susceptible to virulent bacterial strain Pseudomonas syringae pv. tomato DC3000 carrying HopZ5, Col-0 is resistant despite the lack of an HR. We show that HopZ5, like other members of the YopJ superfamily of acetyltransferases that it belongs to, autoacetylates lysine residues. Through comparisons to other family members, we identified an acetyltransferase catalytic activity and demonstrate its requirement for triggering defence in Arabidopsis and Nicotiana species. Collectively, data herein indicate that HopZ5 is a plasma membrane-localized acetyltransferase with autoacetylation activity required for avirulence.

Pseudomonas syringae pv. actinidiae Type III Effectors Localized at Multiple Cellular Compartments Activate or Suppress Innate Immune Responses in Nicotiana benthamiana

“…The number of modules for each effector and their 4 bp Bsa I overhangs are listed in Supplementary Table S1 . All modules for a given effector were then assembled with a C-terminal 6xHA-tag module into the Golden Gate-compatible derivative of the broad host-range vector pBBR1MCS-5, which carries the bacterial avrRps4 promoter ( Jayaraman et al, 2017 ); or with a C-terminal YFP-tag module into the binary vector pICH86988 under control of a cauliflower mosaic virus (CaMV) 35S promoter for functional analysis.…”

“…HopM1 localized to the chloroplasts, while HopAV1 and HopAZ1 localized to the cytoplasm but in strands resembling the cytoskeleton ( Figure 1 and Supplementary Figure S2 ). Eleven effectors localized to the cell periphery (largely absent from cytoplasmic strands), and two of them (HopT1 and AvrE1) showed punctate localization ( Figure 1 ) ( Jayaraman et al, 2017 ). However, we could not determine the subcellular localization of HopAS1, HopW1, and HopX1 in our experimental conditions.…”

An rpw8 quadruple mutant of Arabidopsis Col-0 is partially compromised in bacterial and fungal resistance

“…In contrast, activation of the NLR pair RRS1/RPS4 induces PR1 to ~12x the level of EF1α (Castel et al, 2019a). Autoimmune Arabidopsis mutants expressing the effector hopZ5 show PR1 expression levels of ~3 to ~260 time more than EF1α (Jayaraman et al, 2017). Thus, the autoimmunity of Col-0_rpw8 is detectable but very low.…”

“…B. PR1 expression is elevated in three independent Col-0_rpw8 lines. The expression level is low compared to the PR1 expression levels in a strong autoimmune mutant or upon NLR activation of WT plants (Jayaraman et al, 2017;Castel et al, 2019a). Each bar represents an individual plant.…”

Perturbations of a Kinase-Pseudokinase Module Activate Plant Immunity

“…HopZ1a is a member of a large and diverse family of bacterial effector proteins with similarity to the YopJ effector from Y. pestis . YopJ-like effectors are produced by a variety of pathogens of both plants and animals, and even among P. syringae strains there are five recognized distinct lineages of HopZ effectors (HopZ1 through HopZ5) [58,59]. This inter-allelic sequence variation confers significant functional differences, since only HopZ1a is capable of inducing ETI in Arabidopsis .…”