Mutualistic Co-evolution of Type III Effector Genes in Sinorhizobium fredii and Bradyrhizobium japonicum

PLoS Pathogens

Joel L. Sachs¹  Jeff H. Chang²  Yuan Jiang²  Jeffrey A. Kimbrel²  Caitlin A. Thireault³  Allison L. Creason⁴  William J. Thomas⁴ 

[1] Center for Genome Research and Biocomputing, Oregon State University, Corvallis, Oregon, United States of America;Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, United States of America;Department of Statistics, Oregon State University, Corvallis, Oregon, United States of America;Molecular and Cellular Biology Program, Oregon State University, Corvallis, Oregon, United States of America

关键词: Pseudomonas syringae;    Legumes;    Evolutionary genetics;    Plant pathogens;    Secretion systems;    Host-pathogen interactions;    Sequence alignment;    Conservation genetics;   

DOI  :  10.1371/journal.ppat.1003204

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Two diametric paradigms have been proposed to model the molecular co-evolution of microbial mutualists and their eukaryotic hosts. In one, mutualist and host exhibit an antagonistic arms race and each partner evolves rapidly to maximize their own fitness from the interaction at potential expense of the other. In the opposing model, conflicts between mutualist and host are largely resolved and the interaction is characterized by evolutionary stasis. We tested these opposing frameworks in two lineages of mutualistic rhizobia, Sinorhizobium fredii and Bradyrhizobium japonicum. To examine genes demonstrably important for host-interactions we coupled the mining of genome sequences to a comprehensive functional screen for type III effector genes, which are necessary for many Gram-negative pathogens to infect their hosts. We demonstrate that the rhizobial type III effector genes exhibit a surprisingly high degree of conservation in content and sequence that is in contrast to those of a well characterized plant pathogenic species. This type III effector gene conservation is particularly striking in the context of the relatively high genome-wide diversity of rhizobia. The evolution of rhizobial type III effectors is inconsistent with the molecular arms race paradigm. Instead, our results reveal that these loci are relatively static in rhizobial lineages and suggest that fitness conflicts between rhizobia mutualists and their host plants have been largely resolved.

【 授权许可】

CC BY