title: Spatial gene expression analysis in tomato hypocotyls suggests cysteine as key precursor of vascular sulfur accumulation implicated in Verticillium dahliae defense.
abstract: Verticillium dahliae is a prominent generator of plant vascular wilting disease and sulfur (S)-enhanced defense (SED) mechanisms contribute to its in-planta elimination. The accumulation of S-containing defense compounds (SDCs) including elemental S (S(0) ) has been described based on the comparison of two near-isogenic tomato (Solanum lycopersicum) lines differing in fungal susceptibility. To better understand the effect of S nutrition on V. dahliae resistance both lines were supplied with low, optimal or supraoptimal sulfate-S. An absolute quantification demonstrated a most effective fungal elimination due to luxury plant S nutrition. High-pressure liquid chromatography (HPLC) showed a strong regulation of Cys levels and an S-responsive GSH pool rise in the bulk hypocotyl. High-frequency S peak accumulations were detected in vascular bundles of resistant tomato plants after fungal colonization by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Global transcriptomic analysis suggested that early steps of the primary S metabolism did not promote the SDCs synthesis in the whole hypocotyl as gene expression was downregulated after infection. Enhanced S fertilization mostly alleviated the repressive fungal effect but did not reverse it. Upregulation of glutathione (GSH)-associated genes in bulk hypocotyls but not in vascular bundles indicated a global antioxidative role of GSH. To finally assign the contribution of S metabolism-associated genes to high S(0) accumulations exclusively found in the resistant tomato line, a spatial gene expression approach was applied. Laser microdissection of infected vascular bundles revealed a switch toward transcription of genes connected with cysteine (Cys) synthesis. The upregulation of LeOASTLp1 suggests a role for Cys as key precursor for local S accumulations (possibly S(0) ) in the vascular bundles of the V. dahliae-resistant tomato line.
authors.affiliation: Institute of Plant Nutrition, Leibniz Universität Hannover, Herrenhäuserstraße 2, 30419, Hannover, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Klug
authors.forename: Claudia
authors.initials: C
authors.lastname: Hogekamp
authors.forename: André
authors.initials: A
authors.lastname: Specht
authors.forename: San Shwe
authors.initials: SS
authors.lastname: Myint
authors.forename: Dominik
authors.initials: D
authors.lastname: Blöink
authors.forename: Helge
authors.initials: H
authors.lastname: Küster
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Horst
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D015169:Colony Count, Microbial; D003545:Cysteine / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D056726:Genetic Association Studies; D005838:Genotype; D018546:Hypocotyl / Q000187:drug effects / Q000235:genetics*; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics* / Q000276:immunology / Q000382:microbiology*; D042282:Microdissection; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D058526:Plant Vascular Bundle / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D013054:Spectrophotometry, Atomic; D013431:Sulfates / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*; D020172:Verticillium / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D052584:Xylem / Q000382:microbiology
chemical_list: D013431:Sulfates; D013438:Sulfhydryl Compounds; D013455:Sulfur; D003545:Cysteine