Dynamic Evolution of Pathogenicity Revealed by Sequencing and Comparative Genomics of 19 Pseudomonas syringae Isolates

PLoS Pathogens

Corbin D. Jones¹  Sarah R. Grant²  David A. Baltrus²  M. Shahid Mukhtar²  Jeff H. Chang²  Karen Cherkis²  Marc T. Nishimura²  Jeffery L. Dangl²  Artur Romanchuk²  Jeff Roach³ 

[1] Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America;Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America;Research Computing Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America

关键词: Pseudomonas syringae;    Phylogenetics;    Sequence alignment;    Evolutionary genetics;    Virulence factors;    Genome evolution;    Sequence assembly tools;    Comparative genomics;   

DOI  :  10.1371/journal.ppat.1002132

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Closely related pathogens may differ dramatically in host range, but the molecular, genetic, and evolutionary basis for these differences remains unclear. In many Gram- negative bacteria, including the phytopathogen Pseudomonas syringae, type III effectors (TTEs) are essential for pathogenicity, instrumental in structuring host range, and exhibit wide diversity between strains. To capture the dynamic nature of virulence gene repertoires across P. syringae, we screened 11 diverse strains for novel TTE families and coupled this nearly saturating screen with the sequencing and assembly of 14 phylogenetically diverse isolates from a broad collection of diseased host plants. TTE repertoires vary dramatically in size and content across all P. syringae clades; surprisingly few TTEs are conserved and present in all strains. Those that are likely provide basal requirements for pathogenicity. We demonstrate that functional divergence within one conserved locus, hopM1, leads to dramatic differences in pathogenicity, and we demonstrate that phylogenetics-informed mutagenesis can be used to identify functionally critical residues of TTEs. The dynamism of the TTE repertoire is mirrored by diversity in pathways affecting the synthesis of secreted phytotoxins, highlighting the likely role of both types of virulence factors in determination of host range. We used these 14 draft genome sequences, plus five additional genome sequences previously reported, to identify the core genome for P. syringae and we compared this core to that of two closely related non-pathogenic pseudomonad species. These data revealed the recent acquisition of a 1 Mb megaplasmid by a sub-clade of cucumber pathogens. This megaplasmid encodes a type IV secretion system and a diverse set of unknown proteins, which dramatically increases both the genomic content of these strains and the pan-genome of the species.

【 授权许可】

CC BY