title: Transcriptional profiling of arbuscular mycorrhizal roots exposed to high levels of phosphate reveals the repression of cell cycle-related genes and secreted protein genes in Rhizophagus irregularis.
abstract: The development of arbuscular mycorrhiza (AM) is strongly suppressed under high-phosphate (Pi) conditions. To investigate AM fungal responses during the suppression of AM by high Pi, we performed an RNA-seq analysis of Rhizophagus irregularis colonizing Lotus japonicus roots at different levels of Pi (20, 100, 300, and 500 μM). AM fungal colonization decreased markedly under high-Pi conditions. In total, 163 fungal genes were differentially expressed among the four Pi treatments. Among these genes, a cell cycle-regulatory gene, cyclin-dependent kinase CDK1, and several DNA replication- and mitosis-related genes were repressed under high-Pi conditions. More than 20 genes encoding secreted proteins were also downregulated by high-Pi conditions, including the strigolactone-induced putative secreted protein 1 gene that enhances AM fungal colonization. In contrast, the expression of genes related to aerobic respiration and transport in R. irregularis were largely unaffected. Our data suggest that high Pi suppresses the expression of genes associated with fungal cell cycle progression or that encode secreted proteins that may be required for intercellular hyphal growth and arbuscule formation. However, high Pi has little effect on the transcriptional regulation of the primary metabolism or transport in preformed fungal structures.
authors.affiliation: Department of Bioscience and Food Production Science, Interdisciplinary Graduate School of Science and Technology, Shinshu University, Minamiminowa, Nagano, 399-4598, Japan.
authors.forename: Yusaku
authors.initials: Y
authors.lastname: Sugimura
authors.affiliation: Faculty of Agriculture, Shinshu University, Minamiminowa, Nagano, 399-4598, Japan. saitok@shinshu-u.ac.jp.|Research Center for Fungal & Microbial Dynamism, Shinshu University, Minamiminowa, Nagano, 399-4598, Japan. saitok@shinshu-u.ac.jp.
authors.forename: Katsuharu
authors.identifier: http://orcid.org/0000-0003-2557-1726
authors.initials: K
authors.lastname: Saito
mesh_terms: D002453:Cell Cycle / Q000187:drug effects*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D055137:Glomeromycota / Q000187:drug effects* / Q000378:metabolism; D038821:Mycorrhizae / Q000502:physiology*; D010710:Phosphates / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D059467:Transcriptome / Q000187:drug effects*
chemical_list: D005656:Fungal Proteins; D010710:Phosphates
keywords: Cell cycle progression; Histone; Lotus japonicus; RNA-seq; Secreted protein; Transporter