Transcriptome Analysis of Arbuscular Mycorrhizal Roots during Development of the Prepenetration Apparatus

• Published in: Plant physiology (Bethesda) Vol. 144; no. 3; pp. 1455 - 1466
• Main Authors: Siciliano, Valeria, Genre, Andrea, Balestrini, Raffaella, Cappellazzo, Gilda, deWit, Pierre J.G.M, Bonfante, Paola
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01-07-2007; American Society of Plant Physiologists
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Complementary DNA; defective mutant; DNA Primers; Economic plant physiology; Epidermal cells; Expressed Sequence Tags; expression; Fundamental and applied biological sciences. Psychology; Fungi; Gene Expression Profiling; Gene Library; Genes; Genes, Plant; Genotype; Gigaspora margarita; In Situ Hybridization; legume; Medicago truncatula; Medicago truncatula - microbiology; Medicago truncatula - physiology; Microscopy, Confocal; Molecular Sequence Data; Mutation; Mycorrhizae - physiology; plant; Plant Epidermis - metabolism; Plant Epidermis - physiology; Plant interaction; Plant Proteins - metabolism; Plant roots; Plant Roots - microbiology; Plant Roots - physiology; Plants; Plants Interacting with Other Organisms; Polymerase chain reaction; protein-kinase; Symbiosis; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Symbiosis - physiology; Up regulation; Root; Development; Mycorrhiza
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.107.097980

Information on changes in the plant transcriptome during early interaction with arbuscular mycorrhizal (AM) fungi is still limited since infections are usually not synchronized and plant markers for early stages of colonization are not yet available. A prepenetration apparatus (PPA), organized in epidermal cells during appressorium development, has been reported to be responsible for assembling a trans-cellular tunnel to accommodate the invading fungus. Here, we used PPAs as markers for cell responsiveness to fungal contact to investigate gene expression at this early stage of infection with minimal transcript dilution. PPAs were identified by confocal microscopy in transformed roots of Medicago truncatula expressing green fluorescent protein-HDEL, colonized by the AM fungus Gigaspora margarita. A PPA-targeted suppressive-subtractive cDNA library was built, the cDNAs were cloned and sequenced, and, consequently, 107 putative interaction-specific genes were identified. The expression of a subset of 15 genes, selected by reverse northern dot blot screening, and five additional genes, potentially involved in PPA formation, was analyzed by real-time reverse transcription-polymerase chain reaction and compared with an infection stage, 48 h after the onset of the PPA. Comparison of the expression profile of G. margarita-inoculated wild type and the mycorrhiza-defective dmi3-1 mutant of M. truncatula revealed that an expansin-like gene, expressed in wild-type epidermis during PPA development, can be regarded as an early host marker for successful mycorrhization. A putative Avr9/Cf-9 rapidly elicited gene, found to be up-regulated in the mutant, suggests novel regulatory roles for the DMI3 protein in the early mycorrhization process.