title: Tracking nickel-adaptive biomarkers in Pisolithus albus from New Caledonia using a transcriptomic approach.
abstract: The fungus Pisolithus albus forms ectomycorrhizal (ECM) associations with plants growing on extreme ultramafic soils, which are naturally rich in heavy metals such as nickel. Both nickel-tolerant and nickel-sensitive isolates of P. albus are found in ultramafic soils in New Caledonia, a biodiversity hotspot in the Southwest Pacific. The aim of this work was to monitor the expression of genes involved in the specific molecular response to nickel in a nickel-tolerant P. albus isolate. We used pyrosequencing and quantitative polymerase chain reaction (qPCR) approaches to investigate and compare the transcriptomes of the nickel-tolerant isolate MD06-337 in the presence and absence of nickel. A total of 1,071,375 sequencing reads were assembled to infer expression patterns of 19,518 putative genes. Comparison of expression levels revealed that 30% of the identified genes were modulated by nickel treatment. The genes, for which expression was induced most markedly by nickel, encoded products that were putatively involved in a variety of biological functions, such as the modification of cellular components (53%), regulation of biological processes (27%) and molecular functions (20%). The 10 genes that pyrosequencing analysis indicated were induced the most by nickel were characterized further by qPCR analysis of both nickel-tolerant and nickel-sensitive P. albus isolates. Five of these genes were expressed exclusively in nickel-tolerant isolates as well as in ECM samples in situ, which identified them as potential biomarkers for nickel tolerance in this species. These results clearly suggest a positive transcriptomic response of the fungus to nickel-rich environments. The presence of both nickel-tolerant and nickel-sensitive fungal phenotypes in ultramafic soils might reflect environment-dependent phenotypic responses to variations in the effective concentrations of nickel in heterogeneous ultramafic habitats.
authors.affiliation: IRD, UMR040 LSTM, Centre IRD, BPA5, Promenade Roger Laroque, 98848 Nouméa Cedex, New Caledonia, France. clarisse.majorel@ird.fr
authors.forename: Clarisse
authors.initials: C
authors.lastname: Majorel
authors.forename: Laure
authors.initials: L
authors.lastname: Hannibal
authors.forename: Marie-Estelle
authors.initials: ME
authors.lastname: Soupe
authors.forename: Fabian
authors.initials: F
authors.lastname: Carriconde
authors.forename: Marc
authors.initials: M
authors.lastname: Ducousso
authors.forename: Michel
authors.initials: M
authors.lastname: Lebrun
authors.forename: Philippe
authors.initials: P
authors.lastname: Jourand
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D001487:Basidiomycota / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D044822:Biodiversity; D015415:Biomarkers; D017753:Ecosystem; D015966:Gene Expression Regulation, Fungal; D014644:Genetic Variation; D058977:Molecular Sequence Annotation; D038821:Mycorrhizae / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D009510:New Caledonia; D009532:Nickel / Q000378:metabolism / Q000494:pharmacology*; D010802:Phylogeny; D010944:Plants / Q000382:microbiology; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D059467:Transcriptome
chemical_list: D015415:Biomarkers; D009532:Nickel