Distinctive Gene Expression Profiles and Effectors Consistent With Host Specificity in Two Formae Speciales of Marssonina brunnea

Abstract

The knowledge on the host specificity of a pathogen underlying an interaction is becoming an urgent necessity for global warming. In this study, the gene expression profiles and the roles of effectors in host specificity were integrally characterized with two formae speciales, multigermtubi and monogermtubi, of a hemibiotrophic pathogen Marssonina brunnea when they were infecting respective susceptible poplar hosts. With a functional genome comparison referring to a de novo transcriptome of M. brunnea and Pathogen-Host Interaction database functional annotations, the multigermtubi strain showed abundant and significant differentially expressed unigenes (DEGs) (more than 40%) in colonizing the initial invasion stage and in the necrotrophic stage. The monogermtubi strain induced less than 10% of DEGs in the initial invasion stage but which abruptly increased to more than 80% DEGs in the necrotrophic stage. Both strains induced the least DEGs in the biotrophic stage compared to the initial invasion and necrotrophic stages. The orthologs of the effector genes Ecp6, PemG1, XEG1, ACE1, and Mg3LysM were exclusively induced by one of the two formae speciales depending on the infection stages. Some unigenes homologous to carbohydrate lytic enzyme genes, especially pectate lyases, were notably induced with multigermtubi forma specialis infection but not expressed in the monogermtubi forma specialis at an earlier infection stage. The extraordinary differences in the functional genome level between the two formae speciales of M. brunnea could be fundamental to exploring their host specificity determinant and evolution. This study also firstly provided the fungal transcriptome of the monogermtubi forma specialis for M. brunnea.

Genetic variation along an altitudinal gradient in the Phytophthora infestans effector gene Pi02860

“…They are mainly involved in the regulation of the host’s immunity system but also take part in nutrient uptake of pathogens from hosts ( Uhse and Djamei, 2018 ). To broaden their host range and increase their successful colonization and reproduction, both expression level and profile of pathogen effector genes are strictly regulated during antagonistic interactions, and show waves of concerted expression at diverse stages of infection and reproduction according to the surrounding environment and genetic background of hosts ( Wang et al, 2011 ; Soyer et al, 2014 ; Ren et al, 2020 ). For example, some effector genes are upregulated to promote host susceptibility ( Boevink et al, 2016 ) and subdue the host immune system ( Turnbull et al, 2017 ), while others are down regulated to avoid host recognition ( Lo Presti et al, 2015 ).…”

Editing Metabolism, Sex, and Microbiome: How Can We Help Poplar Resist Pathogens?

“…For example, in 1994, the poplar qualitative resistance gene RMlp7 ceased to confer resistance to some genotypes of rust fungi because a major deletion occurred in the genome of M. larici-populina in the region of the AvrMlp7 effector to which RMlp7 binds [258]. Similarly, M. brunnea has genotypes that differ in host specificity due to the transcription of different genes and, in particular, the use of different effectors [259].…”

The responses of poplars to fungal pathogens: A review of the defensive pathway

“…The results showed there were more differentially expressed genes in the necrotrophic stage than biotrophic stage when poplars infected with M. brunnea . In particular, pectinlyase was significantly induced in multi-strain infections during the initial invasion phase, but not expressed in monoculture infections ( Ren et al., 2020 ).…”