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Divergent and convergent modes of interaction between wheat and Puccinia graminis f. sp. tritici isolates revealed by the comparative gene co-expression network and genome analyses
- Rutter, William B., Salcedo, Andres, Akhunova, Alina, He, Fei, Wang, Shichen, Liang, Hanquan, Bowden, Robert L., Akhunov, Eduard
- Biomed Central (BMC) Genomics 2017 v.18 no.1 pp. 291
- Puccinia graminis, fungal diseases of plants, fungi, gene expression, gene ontology, genes, genomics, host plants, host-pathogen relationships, pathogens, virulence, wheat
- Two opposing evolutionary constraints exert pressure on pathogens: one to diversify virulence factors in order to evade host defenses, and the other to retain virulence factors critical for maintaining a compatible interaction. To better understand how the diversified arsenals of fungal genes promote interaction with the same compatible wheat host, we performed a comparative genomic analysis of two North American isolates of Puccinia graminis f. sp. tritici (Pgt). The patterns of inter-isolate divergence in the secreted candidate effector genes were compared with the levels of conservation and divergence of host-pathogen gene co-expression networks (GCN) developed for each isolate. Gene Ontology (GO) analyses of the conserved and unique parts of the isolate-specific GCNs identified a number of conserved host pathways targeted by both isolates. Interestingly, the degree of inter-isolate sub-network conservation varied widely for the different host pathways and was positively associated with the proportion of conserved effector candidates associated with each sub-network. While different Pgt isolates tended to exploit similar wheat pathways for infection, the mode of host-pathogen interaction varied for different pathways with some pathways being associated with the conserved set of effectors and others being linked with the diverged or isolate-specific effectors. These findings suggest that pathogen populations can maintain diversified sets of effector genes capable of targeting the same host’s biological pathways, thereby creating the basis for diverse virulence strategies that can be utilized by a pathogen to establish compatible interaction with its host.