|Authors: ||M.I. Butler, A. Mazzaglia, L. Gallipoli, G.M. Balestra, R.T.M. Poulter|
|Keywords: ||accessory genome, horizontal transfer, integrative conjugative elements|
Pseudomonas syringae pv. actinidiae (PSA) strains can be grouped into four major groups, Psa1 (Japan), Psa2 (Korea), Psa3 (China, New Zealand, Chile, Europe, Korea) and Psa5, recently described from Japan.
These PSA groups have similar core genomes but have a strikingly diverse repertoire of accessory genomes.
For example, great sequence diversity is shown by the integrative conjugative elements (ICEs). Pac_ICE1 is present in strains from China and New Zealand, Pac_ICE2 is found in strains from China and Europe, Pac_ICE3 is found in strains from China and Chile, Pac_ICE4 is present in strain PA459 (Japan), Pac_ICE5, Pac_ICE6 and Pac_ICE8 have been found only in PSA from China, while Pac_ICE7 is present only in recently isolated strains from Korea.
These ICEs are about 70,000-100,000 bp, occupy one of two lysine tRNA sites in the genome and carry a diverse array of accessory genes and mobile elements.
A large variety of Insertion Sequences (IS) and complex transposons also contribute to the PSA accessory genome.
A plasmid of 74,432 bp can be found in the Psa3 strains, while some Psa3 strains from Korea also carry a plasmid of more than 300,000 bp.
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