Evolution of copper resistance in the kiwifruit pathogen Pseudomonas syringae pv. actinidiae through acquisition of integrative conjugative elements and plasmids

Abstract

Horizontal gene transfer can precipitate rapid evolutionary change. In 2010 the global pandemic of kiwifruit canker disease caused by Pseudomonas syringae pv. actinidiae (Psa) reached New Zealand. At the time of introduction, the single clone responsible for the outbreak was sensitive to copper, however, analysis of a sample of isolates taken in 2015 and 2016 showed that a quarter were copper resistant. Genome sequences of seven strains showed that copper resistance - comprising czc/cusABC and copABCD systems - along with resistance to arsenic and cadmium, was acquired via uptake of integrative conjugative elements (ICEs), but also plasmids. Comparative analysis showed ICEs to have a mosaic structure, with one being a tripartite arrangement of two different ICEs and a plasmid that were isolated in 1921 (USA), 1968 (NZ) and 1988 (Japan), from P. syringae pathogens of millet, wheat and kiwifruit respectively. Two of the Psa ICEs were nearly identical to two ICEs isolated from kiwifruit leaf colonists prior to the introduction of Psa into NZ. Additionally, we show ICE transfer in vitro and in planta, analyze fitness consequences of ICE carriage, capture the de novo formation of novel recombinant ICEs, and explore ICE host-range.

Genomic Structural Variations Affecting Virulence During Clonal Expansion of Pseudomonas syringae pv. actinidiae Biovar 3 in Europe

“…The encoded amino acids sequences whose function could be recognized according to RAST annotation were exclusively phage associated proteins (Table S4 ). Hence, we could find no evidence of gene gain in our sample of 12 European genomes, reveling a picture divergent from that described by Colombi et al ( 2017 ) who showed the acquisition by strains isolated in New Zealand of exogenous integrative conjugative elements carrying copper resistance genes during clonal expansion.…”

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

“…These authors suggested that these distinctive clades are the result of various gene-shifting processes derived from different source populations, hinting at the likely probability of new virulence emergence in Psa populations. In fact, evidence suggests selection driving horizontal gene transfer in a Psa -V strain to gain copper resistance from a local Psa -LV strain ( Colombi et al, 2017 ). Considering the active transfer and conversion events of virulence effector genes in Psa source populations, research efforts on the effector gene pools in geographically co-existing strains such as Psa- LV and Psa- V would be useful.…”

Effect ofBacillus subtilison fruit yield and quality inActinidia deliciosaorchards infected with bacterial canker in the north of Portugal

“…Few of those products reduced disease incidence significantly and consistently (Vanneste, 2013). Today, the industry relies mostly on copper-based products to limit the impact of the disease (Colombi et al, 2017), most of them authorized for winter treatment and effective against other bacterial pathogens on kiwifruit, such as P. syringae pv. syringae and Pseudomonas viridiflava (Fratarcangeli et al, 2010).…”