Gene expression profiling of candidate virulence factors in the laminated root rot pathogen Phellinus sulphurascens

Abstract

BackgroundPhellinus sulphurascens is a fungal pathogen that causes laminar root rot in conifers, one of the most damaging root diseases in western North America. Despite its importance as a forest pathogen, this fungus is still poorly studied at the genomic level. An understanding of the molecular events involved in establishment of the disease should help to develop new methods for control of this disease.ResultsWe generated over 4600 expressed sequence tags from two cDNA libraries constructed using either mycelia grown on cellophane sheets and exposed to Douglas-fir roots or tissues from P. sulphurascens-infected Douglas-fir roots. A total of 890 unique genes were identified from the two libraries, and functional classification of 636 of these genes was possible using the Functional Catalogue (FunCat) annotation scheme. cDNAs were identified that encoded 79 potential virulence factors, including numerous genes implicated in virulence in a variety of phytopathogenic fungi. Many of these putative virulence factors were also among 82 genes identified as encoding putatively secreted proteins. The expression patterns of 86 selected fungal genes over 7 days of infection of Douglas-fir were examined using real-time PCR, and those significantly up-regulated included rhamnogalacturonan acetylesterase, 1,4-benzoquinone reductase, a cyclophilin, a glucoamylase, 3 hydrophobins, a lipase, a serine carboxypeptidase, a putative Ran-binding protein, and two unknown putatively secreted proteins called 1 J04 and 2 J12. Significantly down-regulated genes included a manganese-superoxide dismutase, two metalloproteases, and an unknown putatively secreted protein called Ps0058.ConclusionsThis first collection of Phellinus sulphurascens EST sequences and its annotation provide an important resource for future research aimed at understanding key virulence factors of this forest pathogen. We examined the expression patterns of numerous fungal genes with potential roles in virulence, and found a collection of functionally diverse genes that are significantly up- or down-regulated during infection of Douglas-fir seedling roots by P. sulphurascens.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-603) contains supplementary material, which is available to authorized users.

Identification of effector candidate genes of Rhizoctonia solani AG-1 IA expressed during infection in Brachypodium distachyon

“…Their functions in pathogenicity were also demonstrated in Magnaporthe oryzae , Botrytis cinerea , Cryphonectria parasitica , and Puccinia triticina 41 – 44 . Phellinus sulphurascens , a basidiomycetes pathogen same as R. solani , highly induced a cyclophilin gene during the early stage of root colonization on conifer 45 . Because cyclophilins are involved in plant immunity, loading of pathogen’s cyclophilins into host cells may disturb defense response.…”

Comparative and population genomic landscape of Phellinus noxius: A hypervariable fungus causing root rot in trees

“…However, some fungi are also one of the dominant groups of pathogens causing diseases in trees. There has been an emergence of tree disease outbreaks in different parts of the world such as ash dieback (Gross, Holdenrieder, Pautasso, Queloz, & Sieber, ), Dutch elm disease (Potter, Harwood, Knight, & Tomlinson, ), laminated root rot caused by Phellinus sulphurascens (Williams et al., ) and brown root rot caused by Phellinus noxius (Akiba et al., ; Ann, Chang, & Ko, ; Chung et al., ). Factors contributing to this phenomenon include climate change (Goberville et al., ) and human activity (Fisher et al., ).…”

Genome‐wide gene expression dynamics of the fungal pathogen Dothistroma septosporum throughout its infection cycle of the gymnosperm host Pinus radiata

“…A knowledge of these molecules and their interactions has led directly to the identification and deployment of hosts with increased resistance to these pathogens (Dangl et al, 2013;Vleeshouwers and Oliver, 2014). Most of these studies, however, have concerned the pathogens of angiosperms, and genetic information about how gymnosperm pathogens subdue their hosts and cause disease is only just starting to emerge (Kubisiak et al, 2011;Pendleton et al, 2014;Sniezko et al, 2014;Williams et al, 2014).…”

“…Next-generation sequencing technologies make molecular studies of recalcitrant plant-pathogen systems, such as the pine-Dothistroma system, feasible (McDowell, 2013;Williams et al, 2014), but these are still far from easy. As a result of their large genome sizes (>20 Gb), genome sequencing of conifers remains in its infancy (Neale and Kremer, 2011); in 2013, the conifer Norway spruce (Picea abies) was the first gymnosperm genome to be sequenced (Nystedt et al, 2013), and only one pine genome sequence (Pinus taeda) is publically available today (Zimin et al, 2014).…”